Arsenal 1 Dortmund 2. Lewandowski's late striker steals the points for the visitors. The Gunners not at their best.
One last effort from the Gunners. Gnabry sees a pass down the middle cut out. Arteta then has a shot from distance charged down by Subotic.
Almost there now the visitors. Arsenal look beaten. They look to have run their race.
Arsenal can't get out of their own half. Dortmund doing really well to play out time. Hofmann wins a free-kick down by the corner flag. The ball then slips behind for a corner. Wenger returns to his seat, with the raining pouring down.
Three minutes of stoppage-time to be played.
Dortmund have the ball by the corner flag. Lewandowski can't keep it there, but Arsenal have little option but to lump it long. The ball comes back at them and Koscielny concedes a free-kick. Visitors take their time.
Szczesny almost caught out as he gathers a back-pass. Final change then made by Arsenal as Gnabry comes on in place of Rosicky.
Cazorla with quick feet as he tries to conjure up something. He doesn't stop running and ends up winning a throw wide on the right. Sagna tries to go long, but Hummels climbs highest to nod clear.
Another roll of the dice from Wenger, with Bendtner sent on in place of Ramsey. Meanwhile, Dortmund are looking to lock the door with Reus replaced by Papastathopoulos.
Reus delivers from the set-piece. He whips the ball towards the back post, where Koscielny is on hand to nod clear from in front of his own goal.
Hofmann chooses the wrong option when he has two team-mates up with him. Dortmund remain on the ball and Ozil is cautioned for diving into a tackle on Hummels down by his own corner flag.
Dortmund now looking to play the clock. They are trying to keep the ball away from Arsenal, who have to start pushing men forward. Gaps will open up.
Can Arsenal find a route back into the game once more? They were dominating and will be so frustrated to find themselves behind.
GOAL DORTMUND - LEWANDOWSKI. The visitors regain their lead with a flowing counter-attack. Grosskreutz racing down the right again. He gets his head up and cross to the back post where Lewandowski arrives to crash home on the volley.
Mertesacker and Lewandowski get in a tangle. Decision goes Dortmund's way. They end up going all the way back to their goalkeeper. When the ball is sent forward, Reus fails to find Hofmann.
Sagna with a hanging cross from the right. Giroud gets something on it, but glances on rather than at goal. Cazorla sniffing around the back post, but Weidenfeller drops on the ball in front of him.
Nice one-two between Arteta and Rosicky. Arsenal trying to be a bit too intricate on the edge of the Dortmund box. The Gunners are picking up all of the loose balls now. Visitors running out of energy.
Arteta wide to Ozil, who is playing like an old-fashioned winger now - chalk on the boots. Arsenal get the ball into Giroud, but he can't the ball out of his feet. He goes down, and stays down. He soon bounces back up when he realises Arsenal still have the ball.
Arsenal fans in full voice again. They sense this game is there for the taking. Dortmund are offering little in the final third now. The ball isn't sticking for them. Arsenal looking dangerous when they get the ball wide.
Arteta out to Sagna, who comes inside to Rosicky. He is caught in possession. Lewandowski trying too much again when he has support. He races back to try and make amends, but Ozil picks out Cazorla. He cuts inside on the edge of the box, but sees a shot blocked.
Cazorla draws three yellow shirts to him, before playing a clever pass. His introduction has made Arsenal look a much better outfit. No way through though on this occasion.
Wenger having a word with the fourth official. He isn't convinced by the latest offside call. He soon retreats to his seat. Expect more changes if things stay as they are.
Ball back to Szczesny, who is happy to play the ball out to Koscielny. He goes long, but Giroud can't get anything on it. Flag then goes up against the French striker.
Klopp looks a little fidgety in the stands. He won't be enjoying watching on from afar. His side have started to slip into their shell.
Arteta clips the free-kick wide to Gibbs. He does well to swing a cross around Schmelzer, but he can't find a red shirt. Smart play again by Arteta as he puts in another important challenge, on Aubameyang.
Space for Reus 25 yards from goal, but Arteta slides in to block his path. Arsenal look to counter, but Weidenfeller is alive to the danger and races out of his box to clear from in front of Cazorla. Bender then fells Rosicky and is cautioned.
Ozil combines with Ramsey and cuts the ball back to the edge of the box. Cazorla arrives on cue and sends a well-struck effort over the top after clipping the crossbar. So unlucky.
Ozil twisting and turning down the right again. He finds himself boxed in, but is able to pick out Sagna. Arsenal keeping Dortmund pegged in now.
Aubameyang involved immediately, as Dortmund win a free-kick some 40-odd yards from goal. Sahin swings the ball towards the back post and Hummels. Flag goes up. Poor delivery and poor movement from the German defender.
Double change by Dortmund, with Hofmann and Aubameyang sent on in place of Mkhitaryan and Blaszczykowski.
Ozil forces another corner off Schmelzer. Pressure building from Arsenal. Ozil delivers, Mertesacker nods down and Ramsey lashes into the net. The goal won't count as Koscielny gave Hummels a nudge in the back.
Credit to Koscielny for staying on his feet, but that might have swayed the officials. Anyway, play under way again with Arsenal pushing on. Wilshere has an ice pack on his ankle after taking a seat on the bench. He doesn't look to amused.
Lewandowski cautioned for catching Koscielny with an elbow. His arms were high and he knew the Arsenal man was there. If the referee thought there was any intent, surely he should be off?
Rosicky asks too much of Ozil with a ball down the right. Arsenal decide to look the other way, with Cazorla involved again. Ball being moved around a bit quicker by the hosts now. Cazorla sends a low cross from the dead-ball line into the hands of Weidenfeller.
Gibbs down the left for Cazorla, whose touch lets him down at the vital moment. Arsenal have been a bit hit and miss all evening. Still level, though, and still top of the group.
Ozil takes the corner himself. His whipped delivery is nodded clear by Lewandowski at the front post. Arsenal pick up the loose ball, but go backwards. Rosicky looks to turn defence into attack, but a pass over the top runs through for a goal kick.
Arsenal slow things down by playing across their back four. Dortmund starting to tire a little and aren't pressing as quickly or as high. Ozil able to find a yard of space on the right and combine with Giroud. He wins a corner.
Not Wilshere's best night in fairness. Cazorla offers something a little different. His creativity could be key. He is defending now, though, with Grosskreutz bombing on again. His cross is nodded to safety.
Another misplaced pass from the hosts, this time from Ramsey. Arsenal able to get the ball back quickly. Wenger then makes his first change, with Cazorla sent on in place of Wilshere.
Mkhitaryan crosses from the right. He claims handball as his effort is blocked, but gets nothing. Wilshere looks to send Giroud away with the outside of his boot, but over hits the pass and it runs out for a throw.
Bender slips through the gears and finds Lewandowski wide on the left. He squares for Mkhitaryan, who moves the ball on to Grosskreutz. He is caught in two minds on the edge of the box and sends a tame effort - which was neither a shot nor a cross - into the arms of Szczesny.
Reus runs over halfway, but Giroud tracks all the way back with him. Ramsey gathers, but has no team-mate up with him. Arsenal able to win a throw deep in the Dortmund half. Wilshere sends a cross from the left into the hands of Weidenfeller.
Arsenal try too much in their own half again, but get away with it. Wilshere ends up on the deck and gets the decision. Let off as Dortmund had numbers waiting to spring forward with the loose ball.
Lewandowski spots a run from Reus early. Koscielny gets across the Dortmund man and tries to shield the ball out. He is awarded a free-kick as he is tugged to the deck.
Blaszczykowski sees a pass intended for Reus cut out. Sahin gathers the loose ball, but his crowded out down the right flank. Gibbs able to win a throw. Again, Arsenal make it to halfway. Sagna has to lump the ball long towards no-one.
Mkhitaryan sandwiched between Rosicky and Arteta. The former is shown a yellow card. Dortmund take the free-kick backwards and the ball ends up at the feet of Weidenfeller.
Subotic involved again inside the Arsenal half. Gunners forced very deep. They started the first half slowly, they can't afford a repeat after the interval. They need to force the issue and press higher up the field.
Arsenal fans doing their best to make themselves heard above the away support and inspire their side. Dortmund still controlling proceedings in the middle of the park at the moment. Blaszczykowski felled by Gibbs.
Sahin lobs a pass down the middle. Gibbs deflects the ball away from goal. Lewandowski gathers, but has no support. Arsenal can;t get out of their own half, though. Inviting pressure. Dortmund playing in front of 11 red shirts.
Hummels runs the ball out from the back, before laying off to Subotic. He finds Lewandowski, who has Grosskreutz wide of him. Great challenge from Gibbs as he slides in to block a cross and concede a corner. Reus takes the set-piece short. Wasted.
Schmelzer can't find Lewandowski. Arsenal looking to pick up where they left off, with Ozil well forward. He has Ramsey on the overlap, but his cut back falls behind those in the middle.
Dortmund get the second half under way with no changes made at the interval by either side.
Players back out for the second half and we are ready for the off once more.
Luke says: "I can see a Dortmund win 2-1, Lewandowski."
Conor Sheridan says: "If Arsenal stop passing around their defence and shoots more than they can get a win."
Chris Green says: "Arsenal might have grabbed that all-important equaliser, but I don't think their performance has been convincing so far. The Gunners are going to have to start keeping the ball more as they're giving it away too cheaply at the moment. Dortmund love to capitalise on their opponents' errors, so the Gunners will need to be aware of this as I see Dortmund regaining the lead if Arsenal keep making needless errors at the back."
Remember you can also bet in-play at Skybet.com. Arsenal now 7/4 to take the spoils, with Dortmund and the draw available at the same price. You can get 14/1 on the Gunners to prevail 3-1.
How do you see the second half going? Get your thoughts in to Chris.Burton@bskyb.com or @SkySportsChrisB.
Arsenal 1 Dortmund 1. All square at the interval. The visitors started really well, but the Gunners came back into the game as the half wore on. Still all to play for.
Mkhitaryan gathers in midfield, and has support from Grosskreutz to his right. Another ambitious effort is fired in, which sails high over the top of Szczesny's crossbar from the angle at the top of the penalty area.
Gibbs with a straight ball down the left, but skips off the turf and away from Rosicky. Nice idea. Arsenal don't need to play umpteen passes every time they get the ball - sometimes one is enough. Lewandowski fells Sagna as the pair race towards a loose ball.
Another nice touch from Giroud, off his chest into Wilshere. A man full of confidence this season and one Arsenal need to get into the game more. They aren't taking any chances now, though, with Sagna going back to Mertesacker.
Great time for Arsenal to find a leveller, just before the interval. They need to be careful, though, as Dortmund go looking to re-establish their lead. Reus works the ball onto his right foot on the edge of the box, but curls well wide.
GOAL ARSENAL - GIROUD. All square again. Sagna given acres of space on the right wing. He feeds a cross into the box, and Subotic gets a touch in front of Weidenfeller. The loose ball runs on to Giroud, who smashes into an empty net.
Set-piece floated into the box by Reus. Strange effort deflects off the wall and through to Szczesny. Dortmund moved the ball first, when they had no need to. Could have just put it in the box.
Home fans have found their voice again. Wilshere gives the ball away, though, to bring the groans back. Giroud does down under pressure from Hummels, but is waved back to his feet. Koscielny pulled up at the other end for climbing over Lewandowski.
Ozil touches on towards Giroud, who beats Giroud to a bouncing ball. His cross is cleared to Rosicky, who sees a low drive cleared off the line by Hummels.
Sagna down the line for Wilshere, who turns on towards Ramsey. Hummels there to nod out for Dortmund. Arsenal win a throw. Ball moved to Ramsey, but a back-heel intended for Wilshere is cut out by Schmelzer.
Rosicky sprays a cross-field pass towards Wilshere. He has a lot to do and can only knock the ball out for a throw by the corner flag as he catches up with it. Still no way through for the Gunners.
Dortmund have all bases covered, forcing Arsenal to go long. Wilshere loses possession as he cuts in off the right flank. Grosskreutz feeds Reus, who looks to centre. Szczesny on hand to dive on the ball as it reaches his six-yard box.
Lewandowski pulls out to the right wing. He tries to do it alone, but runs into traffic. With the ball squirming away from him, he ends up tripping Arteta on the edge of the Arsenal box. Some more nervy defending by Dortmund, who don't look as assured at the back now.
Ozil combines with Sagna, who is sprung clear again. He looks to cross first-time, but only has Giroud to aim at in the middle. The delivery sails too close to Weidenfeller, who claims comfortably.
Wilshere back with us. Arsenal fans can breathe a sigh of relief. He looks to be moving okay. Ball with Sagna again, and he finds Wilshere. Patient build-up, with Szczesny brought into play.
Wilshere back on his feet, but not back on the field as yet. Arsenal a man down as they play through midfield. Dortmund won't allow the Gunners any time or space. Koscielny forced out from the back and does really well. Rosicky tees up Ramsey, who drags a 25-yard effort well wide.
Schmelzer well seen off by Mertesacker. Wilshere now getting treatment. He appeared to land awkwardly after trying to jump over Weidenfeller's clearance. He's holding his ankle again.
Wilshere suddenly in behind the Dortmund back four, with Rosicky feeding through a clever lofted pass. Weidenfeller out to meet the Arsenal midfielder, and gets lucky as his clearance hits Wilshere and runs behind. WIlshere goes down off the field.
Grosskreutz forced into a hurried clearance which keeps Arsenal inside the Dortmund half. They can't carve an opening and are relieved to see Lewandowski pulled up for a nudge on Mertesacker as he looks to spin into space.
Weidenfeller firing long again. Lewandowski getting little change out of Mertesacker. He doesn't even both to challenge in the air this time. Arsenal able to send Sagna down the right once more.
Szczesny's long clearance bounces over everyone and through to Weidenfeller. Rare shaky moment for the Dortmund keeper as he almost allows the ball to slip out for a corner. The visitors counter, but Blaszczykowski can't find room for a shot inside a crowded penalty area.
Arsenal growing into the game now. They are seeing more of the ball and have Dortmund pegged back. The visitors do, however, have a lead to protect and have no need to go chasing. As they do push forward, Reus is caught offside.
Flag up again against Giroud. He was off and running again, but went a fraction too soon, Right idea, as he is playing on the line of the last man. Sooner or later he will get one right.
Hummels was booked for his clumsy challenge on Giroud. Ozil over the set-piece. He floats the ball to the back post. Koscielny rises, but sees a header loop behind. He wants a corner, but doesn't get one.
Mertesacker nods safely back to his goalkeeper. Szczesny looks long again, with Sagna glancing down the right for Giroud. He shows great strength to beat Schmelzer, before he is then bundled over right on the edge of the box by Hummels.
Better from Ramsey as he bursts through midfield and gets Arsenal moving. Gibbs is picked out in a promising position on the left, but lets the side down as his cross sails straight out of play. Cause for optimism for the hosts.
Reus popping up all over the place, causing Arsenal problems. An attempted one-two fails to come off on this occasion and the ball runs through to Szczesny. He fires long, but the ball keeps coming back at him.
Sagna with little movement in front of him from a throw. Koscielny then comes through the back of Bender as he tries to keep Arsenal on the front foot. Flag then goes up against Giroud as he tries to spring clear.
Gibbs tracks back well to get a tackle in on Blaszczykowski. Wenger now patrolling the touchline. Not a happy birthday so far for the Arsenal boss. Still plenty of time for the tide to turn.
Arsenal need to raise their game. They have been second best so far and now find themselves behind. Not a situation they are used to this season, but one they have to respond to. Wilshere trying his best, but runs past Schmelzer and out of play.
GOAL DORTMUND - MKHITARYAN. The visitors lead, and Arsenal only have themselves to blame. Ramsey tries to run the ball out on the edge of his own box. Lewandowski picks his pocket and finds Mkhitaryan, who drills into the bottom corner.
Giroud away from Hummels, but reverse pass towards Ozil catches the German off guard. The ball runs behind for a goal kick. Away support still putting on quite a show.
Wayward lump forward from Hummels gives Lewandowski no chance. Arsenal sticking with the footballing game plan. Sagna leading the way again. The Gunners then look to their left, but are again forced to go backwards by Dortmund pressure.
Rosicky pokes on to Sagna, but again Arsenal unable to string anything together inside the Dortmund half. The German outfit look very comfortable at the moment.
Reus into Mkhitaryan. He is well tracked into the box by Gibbs, who gets a toe to the ball. Arsenal can counter at pace. Giroud unable to find a route around Hummels, and now Dortmund can counter. Reus tries his luck from 20 yards out, but sends a curling effort wide of the post.
Sagna bombing down the right. He takes too long to send over a cross and then fails to pick out Ramsey on the overlap. Dortmund win a free-kick and can clear their lines. Visitors the more impressive so far, but no chances to speak of as yet at either end.
Rosicky tripped by Subotic. Chance for Arsenal to piece something together, but they don't. Lewandowski involved again, but is blocked off by Arteta. He wants a free-kick for obstruction, but gets nothing.
Grosskreutz plays a poor pass straight at Gibbs. No out-ball for Arsenal, though. They settle for a throw, but Dortmund are soon back in possession. Lewandowski lays off to Reus, and gets it back. Mertesacker sticks out a leg to prevent him from entering the box.
Lewandowski spins on the edge of the box, but is outnumbered. Sahin dinks onto the head of Schmelzer, but Mertesacker is in the right place again for Arsenal towards the penalty spot. Dortmund seeing a lot of the ball, with the Gunners dropping very deep.
Sagna nods out, but Arsenal can't get on the ball. Dortmund see it safely back to Weidenfeller. Visitors prepared to play their way out from the back. Two sides looking to play the game in the right manner. Who will prevail?
Ramsey runs Arsenal out, but tries too much. Throw to Dortmund in Arsenal territory. Hummels found in space and allowed to drift to within 30 yards of goal. He suffers a rush of blood and hammers an ever-rising effort high into the stands.
Ramsey with a well-timed challenge on Sahin. Dortmund's throw is not the best, but there is no way out for Ozil. Lewandowski looks to feed the ball down the channels for Reus, but Mertesacker comes across to clear inside his own box.
Lewandowski has players getting up with him, including Grosskreutz. He takes aim from 25 yards out, but sweeps a tame effort high, wide and not very handsome. An indication that Dortmund are prepared to push forward in numbers.
Good hold up play by Giroud. Rosicky able to dart forward and is sent tumbling by Bender. Free-kick to Arsenal wide on their left. They take it short and across to Sagna. He settles for a throw off Reus.
Wilshere crunches into a challenge on Mkhitaryan. Free-kick to Dortmund. Arsenal aren't going to take any prisoners either. Set-piece dealt with by Mertesacker. Gunners back on the ball in midfield.
Dortmund look like they intend to press high up the field and give Arsenal no time to slip into their passing stride. Gunners forced backwards on a couple of occasions as they make it over halfway.
Arsenal get us up and running.
Teams out into the arena. Huge roar from both sets of supporters. Game time at the Emirates. Has all the ingredients to be an epic European tussle. Hope it doesn't disappoint.
The players are in the tunnel so we will have to leave the feedback there for now. There will be further opportunities to have your say at half-time and at the final whistle.
Dortmund supporters making their presence felt - win, lose or draw they are going to keep the noise levels up and enjoy their evening. Arsenal will, of course, be hoping to give them little to shout about.
Kevin Dineen is another expecting a nerve-shredding night. He says: "It will be interesting to see how the Gunners adapt without Flamini in the lineup. He has proven to be a great holding midfielder, providing cover for the back four. I fear that we may be exposed unless Ramsey or Arteta are committed to playing a defensive role today. I think it will be a nail biting affair with the Gunners winning 2-0."
Josh Slater sees three points and a clean sheet for the hosts. He says: "2-0 win for the Gunners and in form Ozil and Giroud to get both goals."
Worth pointing out that Jurgen Klopp will be absent from the Dortmund dugout tonight as he serves a touchline ban. Shouldn't mean much, but Arsenal will take any advantage they can get.
Dominic Thomas sees Wenger's men doing the business. He says: "I think Arsenal will win this one with Ozil and Giroud scoring the goals. COYG!"
Half an hour until kick-off at the Emirates. Keep your pre-match thoughts coming in to Chris.Burton@bskyb.com or @SkySportsChrisB.
Chris Clements fears for the Gunners. He says: "I can see tonight being the Lewandowski show, I think the Gunners will be lucky to take a point and can see Dortmund winning 2-1 with Lewandowski scoring both goals."
Chris Green is expecting a tight contest. He says: "Arsenal have impressed me a lot so far this season; they have clearly shown that they have the players to compete in any competition. However, this game is probably going to be their biggest test yet. Dortmund have a good record on their travels in the Champions League, and I reckon they'll trouble Arsenal's defence a lot this evening. The Gunners are the home team and providing that they perform to their full potential, I can't see them having any problems here. However, Dortmund are known for taking early leads, and I hope Arsenal don't allow this to happen as this could be the difference between winning and losing."
Andrew Berragan sees the Gunners getting over the line...just. He says: "Going for an Arsenal win 2-1 with super Ramsey scoring 1st and in form Giroud getting the second. And in typical champ league night style leaving us biting our nails for last 10 minutes. Up the Gunners."
Tonight's referee is Jonas Eriksson from Sweden.
Borussia Dortmund team: Weindenfeller, Grosskreutz, Subotic, Hummels, Schmelzer, Bender, Sahin, Blaszczykowski, Mkhitaryan, Reus, Lewandowski. Subs: Langerak, Kirch, Papastathopoulos, Durm, Hofmann, Aubameyang, Schieber.
Arsenal team: Szczesny, Sagna, Mertesacker, Koscielny, Gibbs, Rosicky, Arteta, Wilshere, Ozil, Ramsey, Giroud. Subs: Fabianski, Vermaelen, Monreal, Jenkinson, Cazorla, Gnabry, Bendtner.
Daniel Dunham is in an excitable mood and hoping for a home win. He says: "I think it will end with an Arsenal win 3-1, playing really good football at the minute and we're in great form. Don't get me wrong Dortmund aren't push overs but will definitely be one of the games to watch tonight. Think Giroud will get the double and a Cazorla goal will win it for the Gunners, Lewandowski for the Dortmund cant wait until kick off. Come on Arsenal !!!!"
You can also bet in-play throughout the evening at Skybet.com. Arsenal start as slight favourites at 11/8, with Dortmund 15/8 and the draw 13/5. You can get Mesut Ozil to score first Price Boosted to 10/1.
How do you see tonight's game going? Feel free to offer your opinion by contacting me direct at Chris.Burton@bskyb.com or @SkySportsChrisB.
The two sides have met on four previous occasions in the Champions League - with Arsenal prevailing on home soil in each of the matches staged in north London.
Dortmund were last season's beaten finalists, but have already dropped three points in Group F and will be aware of the need to establish momentum.
Arsenal have taken maximum points from their opening two fixtures in Europe, and stretched their unbeaten run in all competitions to 12 games over the weekend.
Welcome to Emirates Stadium for our coverage of tonight's UEFA Champions League clash between Arsenal and Borussia Dortmund.