Arsenal easily withstand the late flurry of goalmouth surges from Brighton and can satisfactorily look on towards the next round of the competition.
LuaLua tries hard to get around the outside and get a good ball in towards the far post, but his effort sails out of touch.
The Gunners not pushing up as much as one would expect at this stage of the match, Giroud a lone man up front.
Brighton fighting hard and have four extra minutes to do it, but the Arsenal keep their nerve in the final third.
Mackail-Smith cries foul inside the Gunners' box in the hope of a penalty after the replacement forward fails to get on the end of a long ball in the area.
Brighton withstand a nail-biting barrage on their goalmouth by a Arsenal outfit looking all the better as the match winds down.
Walcott are constant threat now as he breezes into the box from the right and tries to slide the ball past Andergren at the near post, but the Seagulls gloveman makes another fine save.
Brighton being asked again to rally from a goal behind, but time running out, it might be too much to expect of Gus Poyet's men.
GOAL! Walcott fires home with a little deflection from out in front, the England forward in the right place to pounce on the loose ball after a super corner from Podolski.
Giroud, again, on goal and this time forces a corner-kick for the visitors out on the right.
LuaLua with an excellent ball from the left into the danger zone, but Mackail-Smith just can't raise high enough to get his head on the end of it.
Brighton struggling to get their chance on the ball with Arsenal holding their ground.
Giroud can't keep his shot down at the near pos after Podolski does well to feed the two-goal frontman.
Jenkinson with a strong run down the right, but his cross for Podolski out on the far left is too strong.
Arsenal controlling the play with their dominance on the ball, but just can't translate it into another goal.
Santos with a loose shot yet again, and that will be his final contribution as Wenger has clearly has enough and thrown Kieran Gibbs for the closing stages of the match.
Walcott with a quick fire break down the right and into the box, but his dispossessed before he can get his shot off.
Arsenal come again, this time Wilshere on the ball, but he is cleared off the ball before he can really get going.
The Gunners employing the right flank with more regularity with Walcott in particular directing the play for the visitors since his introduction.
Andergren screaming at his defenders to pick Arsenal's movements off the ball as they push up yet again.
Goalscorer Ulloa comes off for Craig Mackail-Smith, but it's Giroud's close encounter from the set-piece spot that has everyone in the stands gasping.
Barnes earns a booking, and gives away a free-kick in a good area, after sloppy challenge.
Arsenal with a swift, flowing movement down the left channel that earns them a corner-kick form the left.
Brighton holds strong on the ball as they launch another promising movement form their own half, only to die down in the final third.
The Seagulls playing from deep with the Gunners throwing Walcot and Wilshere into the front-lines with immediate effect.
Wenger sends on the big guns now, Theo Walcott and Jack Wilshere coming on for Rosicky and Oxlade-Chamberlain.
Giroud and LuaLua tussle for the ball on the halfway line, both desperate to give their side the leg-up on the attack.
Luiz's free-kick form the left for Brighton fails to trouble Arsenal's defensive unit, although play is predominately taking place inside the visitors' half right now.
Brighton with much of the play for the moment as the Gunners drop back on defence in numbers.
Wenger sends the call to his substitutes on the sidelines to get warm as the French tactician maybe looks to make a change soon.
Santos is going to need to more on the right flank as the crosses from the Seagulls are coming in unopposed.
GOAL! Brighton are level again after Ulloa's diving header from the cross from the right beats Szczesny all ends up.
Podolski breaks away down the middle before releasing Rocky, but the midfielder is dispossessed as he was about to shoot from the corner of the box.
Arsenal happy to sit back and catch their opponents on the counter as Brighton are the team needing to hit back sharply.
Magnificent ball from Rosicky for Giroud sees the striker look to complete his hat-trick, but Andergren is up to the task and stops the shot.
The Seagulls not laying down just yet as they battle hard in the centre of the field to poach the ball off the Gunners.
Oxlade-Chamberlain making his way down the right, before whipping in a decent cross, but the cover defence clears his effort with ease.
Back in front on the scoreboard, Arsenal are as eager to extend their lead as Podolski tries to build an attacking foray from the middle of the park.
GOAL! High-quality finish from Giroud at the near post puts the Gunners back in front, the Frenchman controlling the overhead pass with his right before firing home with his left.
Brighton try to catch Arsenal napping on the counter, but Ulloa's shot on the volley from the right his skied out of bounds.
Podolski takes a crack from the set-piece and strikes the crossbar; ever so close for the Gunners.
El-Adb gives away a free-kick out in front for Arsenal.
Gunners with the ascendency as they press up on the break.
Rosicky goes down but the referee waves play on as Carl Jenkinson continues his run and blazes a shot from the right-corner of the box to force a good stop from Ankergren.
Brighton come again, but this time Ramsey manages to get a boot in and disrupt a good passing movement.
LuaLua doing well to weave his way past Diaby on the halfway touchline, but the Gunners invariably force the Seagulls back into their own half.
Santos gets forward but he needs to have put a better ball into the box as Ankergren comfortably gathers.
Arsenal working their way slowly from the back, short passes to-and-fro the method of choice at the moment.
The second half is underway, and Kazenga LuaLua replaces Buckley up front for Brighton.
Rosicky closes out the half with a tame attempt on goal, Birghton likely to be the more satisfied of the two sides heading into the break.
Brighton pushing up in search of a late surprise in stoppage time, but the Arsenal aren't giving away anything at the back at this stage.
Santos with a wasteful shot on goal from some way out and one would be surprised to see him return in the second half.
Nothing comes from the resulting set-piece as the touch official signals three extra minutes of play.
Arsenal with the lion's share of the ball in the latter stages of the first half, Aaron Ramsey's strong run the resulting in a corner-kick out on the left.
The Gunners press again, only for Giroud to lose the ball and then give away a foul trying to regain possession.
Brighton look to catch Arsenal on the counter through Ulloa, but the Seagulls frontman's control lets him down and his easily relieved of the ball.
Ramsey trying to direct play form the centre of the park, but the Seagulls' back-line hold their nerve to dispossess the midfielder before he could unleash a team-mate.
Oxlade-Chamberlain with a great delivery to the near post, but Ulloa does well to head the ball clear on defence.
Brighton on the back-foot for the moment as some good play from Arsenal earns them another corner, this time from the right.
Arsenal continue to press, especially down the right wing through Oxlade-Chamberlain.
Sad sight as Gordon Greer departs with looks to be a hamstring injury, Gary coming on in his stead.
No luck for the Gunners from the set-piece but they earn themselves another one in a similar area moments later.
Arsenal work their way up the park to earn themselves a decent free-kick opportunity from the right.
Great header from Barnes, but the Gunners are making the presence felt again in ana effort to regain the lead.
GOAL! Brighton are now level on terms with Ashley Barnes capitalising on Szczesny's inability to deal with the corner.
Brighton force their way back up field and earn themselves a corner-kick form the right, Santos again struggling to keep up down the flank.
The Seagulls may rue their recent chance to level the score, but it will be the Gunners who should be concerned as Andre Santos was at fault for losing the ball, and really doesn't look to confident overall.
Unlucky Brighton as Ullou puts the ball past Szczesny off the shot-stopper's parry from Buckley's pass into the area, but the linesman's flag is up for offsides.
Diaby and Luiz collide to earn the Gunners a good attacking free-kick just over the halfway line, but the capital outfit fail to make the opportunity count.
Brighton easily deal with Arsenal's corner-kick from the left, but the Gunners keep pressing.
Giroud with a decent cross in from the right that forces the hosts to bang the ball into touch.
Good attacking effort from Brighton, Buckley's ultimate back-heel for Jose Ulloa unable to get the decided result in the goalmouth.
The home side back on the ball, but having to build their attacking play from deep, allowing the visitors to set their defensive line.
Inigo Calderon with a cross-come-shot from the right that wrong-foots Szczesny, but drifts well over the crossbar.
Diaby hoofs the ball up field as Brighton work the ball towards Arsenal's danger area from the right channel.
Arsenal passing the ball around at the back calmly as they look not too rush their next forward thrust.
The Gunners forcing the Seagulls back into their own half having relinquished possession on the halfway line.
Arsenal now with most of the possession as they look to create another scoring opportunity for themselves.
Oxlade-Chamberlain beats Bridge out on the right with his superior pace, but instead of going for goal himself, he sends in a cross for no one to get on the end of.
Arsene Wenger will be a relieved man with his side having gone ahead against the run of play.
GOAL! Giroud rounds off a stunning counter-attack from the Gunners with low drive into the bottom left corner to give the north Londers the lead early on.
Buckley with a shot on goal that draws a reflex save from Wojciech Szczesny, but the flag was up for offsides.
Seagulls making a good account of themselves going forward as they launch yet another surge on goal from the right flank.
Brighton breakout nicely, only for the long ball out to the right for Will Buckley too have too much power on it.
David Lopez goes into the referee's book for trip from behind on Tomas Rosicky.
Arsenal consolidate possession at the back as they aim to build a long-range attacking movement.
Wayne Bridge delivers the ball in from the left, but his pass into the 18-yard area is too long.
The match is evenly poised with both sides seeing a bit of possession.
Abou Diaby looking to get in the middle of the park, only for the defence to shepherd him towards the touchline.
The Gunners fail to really capitalise on their first set-piece of the match, the Seagulls dealing well with the ball into their area from the left.
Alex Oxlade-Chamberlain whips the ball in from the right for Lukas Podolski, but Adam El-Abd clears the ball into touch for a corner.
Seagulls on the attack, but the visitors' back-line clear the danger after a long ball into the box.
Some nervous moments at the back with Casper Ankergren struggling to make his clearance under pressure from Giroud.
Olivier Giroud pushing up in earnest, but the home defence closes him down smartly.
Gunners looking to settle early but the Seagulls are as keen to find their rhythm.
The match is underway!
Feel free to e-mail your thoughts or predictions to email@example.com and we'll publish as many of them before - and during - the game as possible.
Brighton are rated at 21/5 to beat Arsenal today according to our friends at Sky Bet, while it is 3/1 for the match to end in a draw. The Gunners, however, are 8/13 to pick the victory, with Theo Walcott 5/1 to score a brace.
Meanwhile, the Seagulls will be buoyed by their shock 2-0 win over Newcastle in the last round and will look to repeat that upset when another Premier League side comes to town.
The FA Cup represents the Gunners' best chance to end their seven-year trophy drought, with a Jack Wilshere inspired win over Swansea in the third round likely enough to give the north Londoners the confidence on the road.
Good afternoon, I'm Devin Hermanus and I'll be taking you through all the action as Brighton host Arsenal at Amex Stadium. Kick-off is scheduled for 1500 BST.