Full Time. That's it. A 1-1 draw in the Bernabeu sets things up for an intriguing return leg at Old Trafford.
Chance! Anderson loses out to Modric and he does well to cross for Ronaldo. He looks set to pounce but Jones somehow gets the ball away.
Ozil wins a free-kick following a mazy run.
Evra tracks the run from Ronaldo and the ball runs through to De Gea. Time running out for a winner.
88 Valencia booked for a foul on Ramos.
Ronaldo with an ambitious effort from way out but he strikes it astonishingly. De Gea is beaten as the ball dips wildly but it is the roof of the net that is rippling.
84 Anderson on for Rooney.
84 Pepe on for Alonso.
Chance for Giggs to take a snap shot inside the box but for some reason he decides to take a touch and the chance is gone.
Another Real corner.
The ball bobbles around the United box but Khedira looks to be about to fire the home side ahead only for De Gea to cling onto his effort. The German was well placed there.
Khedira wins a corner.
The changes seem aimed at making both sides more solid and United certainly look to be containing Real at present.
75 Modric on for Di Maria.
Ozil shot deflects off Evans for a corner.
73 Valencia for Welbeck.
And then they break! Rooney slips the ball to Van Persie and his stinging shot is saved onto the woodwork by Lopez. Then seconds later Van Persie looks to be offside at first but is well onside... he has time to shoot but scuffs the shot! It still beats Lopez and looks to be bobbling into the net but Alonso gets there to clear off the line.
Pressure building. United struggling to get out of their own half.
Ronaldo blocked by Ferdinand at the near post and that's a corner.
Real continuing to slow the tempo - enjoying the space in front without penetrating the United defence.
Van Persie cuts in from the left but cannot find Evra with his reverse pass.
The delivery is poor though, from Di Maria and then Alonso, and when the ball is finally cleared Welbeck wins a free-kick on the halfway line.
And then all of a sudden Di Maria skins Rooney on the left and wins a corner.
Sting gone out of the game for now. Real wary of the second away goal and United defending in numbers.
64 Giggs on for Kagawa.
The corner comes to nothing as the flag goes up.
Welbeck with a powerful run to get away down the left but Varane manages to block the eventual shot for a corner.
Chance! Slow build-up from Real lets all the United team get behind the ball but Khedira's right-wing cross still manages to find Coentrao at the far post and De Gea clears the slid effort with his feet.
60 Higuain on for Benzema.
Rooney holds the ball up well but Carrick's pass goes astray when trying to put Evra away down the left.
Real so narrow now. Di Maria and Ronaldo almost playing centrally alongside Benzema. It is allowing them to play little one-twos around the United box but the congestion is causing problems too. This time Ronaldo runs into trouble.
Kagawa delays his pass and is robbed by Benzema. Ronaldo gets away but is shepherded wide before Di Maria's eventual shot is deflected to safety.
Varane clears from Van Persie.
Rafael is blocked off and the free-kick is a chance to whip a ball in from the right.
Evra looks to be away in behind Varane and the young defender looks to have fouled his compatriot but the referee gives nothing. Huge decision as Evra was in on goal if he hadn't gone down.
More patient build-up from Real and Di Maria again blasts in a shot from just outside the box. It's well hit and bounces just wide with De Gea motionless.
Di Maria with the shot from distance now but it is right at De Gea who does well to hold onto the ball.
Real putting United under pressure but are a little narrow at present. Ronaldo is fouled by Jones as the visitors try to crowd out the home star.
Driving run from Ozil is thwarted by good tracking from Jones.
Real settle down after a lengthy spell of possession. Khedira feeds the ball into Ronaldo on the edge of the box with his back to goal and he turns to get the shot away but De Gea saves well.
Lopez gets blocked off from the corner and stays on his line. That allows Jones a free header but he doesn't realise the time he has and nods the ball over the bar.
Positive start from United too. Van Persie and Rooney swing crosses under the bar and then the former wins a corner. Lopez under pressure and Welbeck could perhaps have got on the end of one of those chances.
United kick-off and the second half is underway.
Half Time. Fascinating contest is all-square at the break. Welbeck's header cancelled out by one from Ronaldo.
Coentrao with an inviting cross and Ronaldo looks set to head the ball home but can only get a shoulder on it under pressure from Evans.
Corner comes out to Rafael but he is rushed and fires well over.
United break well through Kagawa after good work from Van Persie and it's a United corner.
Ronaldo gives the ball away needlessly but then Arbeloa prevents Evra from breaking and is fortunate not to go in the book.
Good work from Di Maria and Ozil finds Ronaldo in space cutting in from the right and he fires left-footed just over the bar.
Free-kick is wasted by Benzema at the far post and United look to break but Di Maria does brilliantly to rob Van Persie and then beat three. He appeals for a penalty as he tries to beat a fourth in Jones but the referee ignores his pleas.
40 Rafael booked for a foul on Ozil on the byline.
Di Maria with a purposeful run that finds Ozil in space on the left. The German cuts the ball back but cannot find Ronaldo or Benzema despite some panic in the area.
Wonderful pass from Alonso almost gets Ozil away in the right channel and he fires at the near post but De Gea is down to parry the ball away. The corner comes to nothing.
This time Van Persie swings the ball in but Rooney can only head wide under pressure.
Rooney overhits the corner but Rafael wins another one.
Welbeck wins another corner in a race with Varane.
Corner comes to Kagawa whose shot is blocked and then Rooney has space but scuffs a shot wide.
Chance! Van Persie crosses for Welbeck at the near post and the opening goalscorer sticks out a leg but Lopez is down well to smother the effort and smuggle the ball away for a corner.
Mourinho livid after a foul is given against Rooney right in front of him.
Clever turn from Van Persie in the left channel back onto his right but the shot is deflected and runs tamely towards Lopez.
That's raised the crowd but Ozil delays his pass and Ronaldo has to check the run.
Di Maria with the cross from the left, having switched wings with Ronaldo. And his delivery found that man who seemed to hang in the air to steer the ball past De Gea. Evra left flat-footed.
30 Goal! Header from Cristiano Ronaldo!
Ozil gets away from Rafael but the full-back recovers to clear for a throw.
Ronaldo blasts his free-kick into the wall and then volleys left-footed just wide of the post.
Coentrao with a clever forward pass to Ronaldo and Carrick commits the foul.
This corner is cleared.
De Gea with a nervy punch away under no pressure.
Corner for Real.
Free-kick given against Van Persie for handball. Risky move by the forward after that early booking.
Rooney almost threads a ball through to Welbeck but Ramos is there on the cover.
Di Maria with a low shot that De Gea turns round the post.
Jones helps Rafael deal with Ronaldo and the winger has to settle for a throw-in.
United fans making the noise now as the visitors come forward again. Confident start from the English side.
Rooney with the inswinging corner from the left and Welbeck pulls away from Ramos to nod the ball into the far corner.
20 Goal! Danny Welbeck with the header from the corner!
Route one from United. Van Persie with a flick-on from De Gea's long ball and Kagawa wins a corner off Ramos.
Ozil with a good run but his shot from outside the box is blocked.
Patient build-up from Real.
Evans down after a stray elbow from Ramos. But United deal with the corner well in the end.
Ramos nips in ahead of Kagawa and is then pulled back by the Japanese attacking midfielder. Subsequent free-kick brings another Real corner.
But the corner comes to nothing.
Brilliant defending from Varane before springing Ronaldo away. Evans looks to have snuffed out the threat but then concedes a corner.
Good work from Evra to stick with Di Maria and win a free-kick on the right wing. The United skipper certainly man-marked his winger there.
Van Persie's lay-off almost puts Kagawa through via a fortunate ricochet but the ball runs through to Lopez.
Rooney sees his long-range shot deflect off Welbeck to safety.
United look comfortable as Rooney and Rafael double up on Ronaldo but the young full-back lets the winger escape and centre for Benzema but the France international striker sees his shot blocked.
Arbeloa's cross is cleared but Rooney cannot find Van Persie on the break and then Evra fouls Ozil to buy United some time to regroup.
United win a corner after a defensive mix-up but Rafael miskicks when the cross is headed to the edge of the box.
Ronaldo gets space in the centre as the United defence backs off but the Portuguese star scuffs his shot from distance well wide.
Header over the bar from a Real free-kick.
Chance! De Gea with a save onto the post from Coentrao! The full-back shot with his right foot and the ball rolls along the ground across the six-yard box before United clear.
5 Van Persie booked for putting his hand in the face of Ramos as they prepare to contest an aerial challenge.
Di Maria cuts in from the right and fends off the challenge of Evra before firing just wide.
Kagawa just offside as Van Persie attempts a cushioned through-ball.
Rooney tries to put Van Persie through but Lopez is off his line quickly to head clear.
But the first chance is for Real. Khedira gets the ball in a bit of space inside the area but drags his shot wide with his weaker left foot.
Decent possession for the visitors in the early stages.
Real Madrid kick-off and we are underway.
Rooney lining up on the right with Welbeck left as we prepare to kick-off.
Evra and Ramos exchange pleasantries - they are the captains for the night.
The players are on the pitch and the Champions League anthem blares out.
Thanks for all your feedback. We will be underway shortly here as the players are preparing in the tunnel. Huge atmosphere in the Bernabeu.
Nathan: "I can see the game being close. I reckon a 3-2 win for the Reds."
James: "2-2 with Ronaldo and Benzema to score first and then Van Persie and Rooney to get the last two."
Ryan: "Really strong team for United. A good choice Fergie has made. I'm saying 2-0 United."
Liam: "I think it is a good side. Shocked Vidic is not in it and shocked Valencia is not in it but I think United will be happy with a 1-1 draw."
Sam: "I'm 13 and a United fan. Struggle to see why Valencia isn't starting; he's far fitter and a better crosser of the ball than Welbeck. Should have been three up front with Chicharito and a more defensive midfield. 2-1 to Real."
As for Real, Varane is highly-rated but Van Persie is a different test - a player capable of seizing on the slightest mistake from the young defender.
Big night for De Gea back in Madrid. And how about the faith shown in Evans by the United boss?
Ground starting to fill up now as we approach kick-off. Interesting debate about the team selections. Not a lot of love for Welbeck out there but his mobility will surely be important with United expecting to play on the break?
"My name is Thomas I'm 8 and I'm going with 4-2 Madrid with a Ronaldo hat-trick, RVP brace and Benzema scoring once."
Ben: "Real Madrid have been pretty poor this season, with a lot of individual mistakes. A few key injuries, a young centre-half and a vulnerable right back with a midfield duo that do lack in pace. The game is there for United, hence Fergie's offensive team selection. RM 1-2 United tonight."
King Jones all the way from Botswana says: "The debate is high as to who will win this one, i think that you got two great teams with massive talent on either side, there is no saying which side the coin will drop. Madrid have a slight edge playing at home but Man U will be equal to the task. I think if Madrid win it will be by either 1-0 , 2-1 or it will end 0-0. Good luck to both teams."
Matt: "Ferdinand and Evans at the back with no wide cover for the full-backs?! It's gonna get messy! Ronaldo will bully this defence!"
Amit: "I think Madrid will win this 2-1 purely because Madrid need this more than United and with the likes of Ronaldo I can see him completing the job. Hopefully the game will be open so both teams can attack."
Pete: "I have to go with a 5-0 thrashing tonight. United have no chance, they are a one VAN team! Madrid will keep him quiet tonight!"
Ian: "Welbeck? I really don't get why Welbeck starts but Cleverley and Valencia are on the bench. Going to be a tough game tonight!"
Suspect Welbeck and Rooney will be expected to track back and support the full-backs but the onus will be on them to counter-attack too. They have the pace to do it. The question will be whether they have the ball.
Simon: "This is embarrassing. No cover for the full-backs. Ronaldo and Di Maria to run riot here."
Nick: "Kagawa needs to have a good game. Think it will be 1-1."
Sam: "Kagawa, Welbeck, Rooney and RVP all starting? Massive gamble. 3-2 Madrid."
Plenty of attacking options on the bench for both sides this evening. Real have Kaka, Modric and Higuain to call upon, while United have Cleverley, Giggs and Hernandez.
Felix says: "Shock!! Big scoring first leg, 2-4 to United. Can't see a stalemate here - the tie will be decided tonight."
Harish says: "Really happy with the team selection from Sir Alex. Love the way how he is going for an attacking four and Carrick and Jones providing cover. It is really perfect with Carrick linking up defence to attack and Kagawa to take over in the final third. Welbeck and Rooney but no wingers. Lovely stuff. Both Rooney and Welbeck are going to be running all round the park. Probably a bit harsh on Valencia but Sir Alex's strategy is clear and he is going for away goals and a solid presence in the middle of the park. Will be interesting. I think this will be 2-1 to United."
Jay: "I think it'll be 1-1 tonight but surprised there's no Valencia on the right to support Rafael with Ronaldo."
Harry: "I think Manchester United will have a tough challenge tonight but I think they will win 2-1. I think Rooney will score twice."
Lewis: "Madrid are tactically and physically ahead of United so can't see past a Madrid win. United have to hope for no heavy deficit."
Harvey: "I hope United win. I am an Arsenal supporter. But I will support the team from my country. Madrid used to be my Spanish team. But come on United."
Micky: "Welbeck and Ferdinand in starting line up - What a major, major surprise, I was going to say 2-1 to Real....but now it's 4-1 - easier walk in the park!"
No Vidic for United and, as expected, Jones gets the nod in midfield. It's an attacking front four though so Ferguson will be looking to cause problems too. Your thoughts?
Real Madrid (4-2-3-1): Lopez; Arbeloa, Ramos, Varane, Coentrao; Alonso, Khedira; Di Maria, Ozil, Ronaldo; Benzema. Subs: Adan, Pepe, Carvalho, Essien, Kaka, Modric, Higuain.
Man Utd (4-2-3-1): De Gea; Rafael, Evans, Ferdinand, Evra; Jones, Carrick; Welbeck, Kagawa, Rooney; Van Persie. Subs: Lindegaard, Smalling, Valencia, Cleverley, Giggs, Anderson, Hernandez.
Thoughts on Rooney? Be interesting to see where he lines up. Expecting him to play from the left this evening? Vital that Van Persie gets support but United will surely have plenty of defending to do.
Jake: "Ronaldo's time to shine. I think 2-0 Real Madrid with Ronaldo to get both."
Gaz sees it differently though. "I think United will be too strong for Madrid tonight - 3-1 with Rooney running the show."
Gareth has also been in touch to predict a 3-1 Real win.
Numan: "Ronaldo, Benzema and Alonso the scorers for Real Madrid with Rooney grabbing an away goal for Manchester United."
Joe: "I'm going for 2-0 to Real. Ronaldo brace. They aren't going to lose at the Bernabeu."
Agree with that? Rafael has been in fine form this season and has the pace but this is probably the toughest challenge any right-back can face tonight.
Dave: "With Rafael marking Ronaldo a red card and Real to win looks too good to miss."
If you are thinking that means a thrashing for the visitors, consider that Real Madrid have failed to keep a clean sheet in this season's competition. They have conceded nine goals in the Champions League campaign so far, the most among the 16 teams qualified for the knockout stages.
With the talent on offer, goals look a good bet this evening. The eight European Cup/Champions League encounters between Real Madrid and Manchester United have produced 31 goals (3.9/game).
Alan: "I'm thinking 2-0 to Real Madrid no matter how much it'd be good to see United do well, but sorry just can't see it: Real will be primed for it as nothing else left for them domestically this year."
Jack: "I can see United nicking this one. I'm going for Wayne Rooney to score any time and United to win. 7/1 on Sky Bet."
United would surely take a draw tonight with a score draw putting them in the driving seat. Ferguson's men have drawn seven of their 13 Champions League ties in Spain.
Our friends at Sky Bet have the odds for this one. Real Madrid are 3/5 favourites to win the first leg this evening with Manchester United the 4/1 underdogs. The draw is available at 7/2.
Gareth: "I reckon United will scrape it 2-1. Van Persie to score the winner."
John: "It's going to be a win for United as their players are on form but it's going to be a tough one."
Ollie: "I think Ronaldo will run riot and it will be 3-0."
Paul: "My prediction for tonight is RVP first goal and result to be 1-1. Got 50/1 for that scorecast on Sky Bet. It's only 40s or less elsewhere."
Jamie: "Going to be tough for United tonight. I can see a 3-1 victory for Madrid with Ronaldo on the scoresheet."
Jamal says: "Just want to say everyone is talking about how much of a threat Ronaldo is going to be but I believe the damage is going to come from other players like Benzema. But nevertheless I think we're going to take it 2-3."
The teams have not been confirmed yet but Ferguson has already revealed who will be the player tasked with keeping Ronaldo quiet. "The responsibility will be with Rafael," Ferguson told MUTV. "Rafael's maturity this season has been fantastic."
Any thoughts or predictions ahead of this one? Let me know by email at firstname.lastname@example.org or on Twitter @GhostGoal.
And there are match-winners in the United line up too. Robin van Persie has found the net in all but three of the club's last 14 games. And all three of his Champions League goals this season have come away from home.
Cristiano Ronaldo takes on his former club and is in outrageous form of late, having scored 10 goals in his last five games.
Plenty of the focus will be on the teams' high-profile managers Sir Alex Ferguson and Jose Mourinho. But there are a number of world-class players capable of taking the headlines too...
This is the one that everyone has been waiting for between two of the world's biggest clubs.
Welcome to live and interactive text commentary of Real Madrid against Manchester United in the last 16 of the UEFA Champions League.
Kick-off is 1945 GMT.