FULL TIME. Barcelona 2 Real Madrid 2.
Barca are finishing strong as Pedro's effort clips the heel of Sanchez and incredibly lands wide of goal as it trickled away from the far post.
With two minutes of added time to be played, Barca play a patient game as Arbeloa defends well under Messi's threat near the byline.
Xavi's effort is tipped over the bar by the Madrid wall and the hosts have a late chance to win this from the corner.
Messi is clattered into by Arbeloa, a yellow card for the defender, and a free-kick 20 yards out for Barca.
Montoya hits the bar! His curling shot from the edge of the box is desperately unlucky not to give Barca back the lead as a resulting corner is cleared by the visitors.
Another change for Madrid as Essien comes on in place of Di Maria.
Sublime skill from Sanchez lures in Alonso, who again runs the risk of a second yellow card and again, nothing is given.
Higuain's cross takes a wicked deflection off Mascherano but ends up safely away from goal as Barca break. Pedro only ventures as far as Kaka though who makes a crucial interception.
Alonso teases the ball to the far post but Higuain's shocking control sees the ball stabbed behind goal when a knock back into the box was fairly simple to achieve.
Ronaldo powers his way through down the left, and Montoya ends up conceding the free-kick after holding back the Madrid forward.
Pepe ends up doing splendidly to head away the danger, but Barca attack again through Sanchez who is caught offside in a rather harsh decision.
Pepe looks to help a long ball back to Casillas but ends up conceding a corner which Xavi will take.
Ozil's game is over as Kaka comes off for Madrid.
Sanchez controls the bal with his hand and after impressive movement from the striker, a free-kick is given.
Messi takes a tumble under Pepe but the offside flag is raised due to Alba's storming run on the left.
Di Maria carelessly plays Madrid into trouble after wonderful work initially from Ozil. Pepe then earns a yellow card for a tug on Messi.
Higuain hops to the byline and fires at the near post to force a solid save in the end from Valdes.
Messi, also in search of a hat-trick, takes aim, but this time directs his free-kick into the sponsor boards behind goal.
Messi eventually draws a free-kick after some persistant nagging from Arbeloa. A tad harsh on the Madrid defender.
Good chance again for Barca. Iniesta and Messi do splendidly before the former chips the ball across goal forcing an excellent clearance from Marcelo.
The tempo has slowed somewhat as Barca try to patiently work the ball forward, Madrid seem comfortable though as they focus their energies on hitting Barca on the break.
Xavi and Iniesta play starring roles in a lovely move that Busquets ruins, before hacking down Khedira to concede a foul.
Big chance for Barca. Alba makes a wonderful run and cuts back to Messi who scoops a left-footed effort slightly wide of goal.
Ronaldo is back up but still in some obvious distress - with Mourinho no doubt fearing the worst as his best player could be heading for an early bath here.
Ronaldo, seeking his hat-trick, fires on the edge of the area but Adriano sticks his body in the way as Ronaldo then goes down clutching that injured shoulder.
It's Messi 2 Ronaldo 2. What Messi can do Ronaldo can do too as Ozil finds his run and Ronaldo calmly finishes past Valdes. It's all square again!
GOAL FOR REAL MADRID - RONALDO!
Ronaldo attempts an overhead kick from the corner, fails to make contact, and lands painfully on his shoulder. Incredible scenes.
Ozil plays a neat one-two with Di Maria, earning a corner for his efforts as Montoya cuts out his cross from the right.
Sanchez comes on for Barca with Fabregas the man replaced.
Busquets tumbles under Khedira, and Pepe is far too animated as he speaks to the referee, with fortunately no yellow card shown.
Benzema is hauled off as Higuain takes his place for Madrid.
What a goal. Messi puts Barca ahead with a simply divine free-kick. His technique is incredible and once again he makes a memorable stamp on El Clasico. Barca have turned the game around!
GOAL FOR BARCELONA - MESSI!
The players are surrounding the referee after Alonso's challenge on Messi, with calls for the dismissal of the Madrid midfielder.
Messi does excellently but doesn't win a throw-in after a valiant battle for possession with Arbeloa down the right.
Fabregas managers to drive a wicked delivery across the face of goal, with Casillas more than relieved to see it flash through with no-one getting a touch to it.
Busquets is hacked down but the referee lets play continue. Madrid end up breaking but Montoya is again on hand to intercept from Ozil.
Ronaldo hits his own player in the free-kick as Pepe takes a clattering. Real have a throw-in on the right side but Ozil loses control and Alba regains possession.
Busquets chops down Ronaldo cynically and Madrid have a free-kick roughly 30 yards out, with the midfielder receiving a booking as a result.
Montoya intercepts Khedira's pass but at the other end of the field Arbeloa does well against Messi.
Iniesta draws the foul from Pepe inside the penalty area and incredibly, a free-kick is given. Nothing comes of it and now both teams have grievances over penalty decisions that should have gone their way.
Mascherano plays a lovely ball into Pedro, who twists and turns, and eventually crosses in where a brave leap from Pepe sees the ball cleared.
Ozil classily turns away from Montoya as Madrid make a bright start to the second half, before Fabregas dispossess Khedira.
There's a heart-in-mouth moment for Pepe as he deflects Iniesta's strike which fortunately lands in the hands of Valdes. Moments later, Adriano handles and concedes a free-kick 30-yards from goal.
Ozil turns past Montoya in the penalty area and looks to be tripped. No penalty is given and suffice to say the Madrid camp are not happy.
Barcelona get the game back underway.
A half riddled with mistakes is capped off by a couple of scrappy goals that ensure things are level at the break. It's been fascinating, and you can send your second half predictions to email@example.com
HALF TIME. Barcelona 1 Real Madrid 1.
Alba does brilliantly, before Iniesta is stopped in his tracks after terrific defending from Pepe.
Yellow card for Alonso now for clipping the heels of Xavi, with the bookings starting to fly thick and fast now.
Marceloa finds Di Maria, who first touch was perfect, but second touch gives it straight to Xavi.
Alba isn't doing himself any favours though as he overzealously goes in Busquets, who of course makes quite the meal of the tackle.
Arbeloa is very much trying to get Alba sent off by the looks of it, as he claims a foul against the defender before vehemently protesting to the referee.
Ramos and Pedro clash in a 50-50 challenge and Pedro collects the yellow card, perhaps slightly harshly.
Alba shows a tad too much enthusiasm as he rattles through Arbeloa who was trying to usher the ball out of play. Arbeloa makes the most of it, but it was certainly a foul.
Pedro has looked very lively on the right, and as Barca press he is playing an integral role in any attacking movement.
Xavi's uncharacteristically poor pass ends up with Alonso, but credit to Fabregas who wins it back for his side.
Iniesta takes a tumble under Khedria but despite loud cries from the Catalan faithful, no foul is given.
Ronaldo's incredible stepover fools Montoya, with Mascherano then going in two-footed on the magician to concede a foul.
A rush of blood to Casillas' head sees him try to fool Messi - the Madrid keeper barely getting away with it as he boots the ball away.
The two best both players are both on the scoresheet after just 30 minutes. Pedro's ball takes an unfortunate touch off Pepe, allowing Messi home to stab home from close range. 1-1 and game on again!
GOAL FOR BARCELONA - MESSI!
A rather poor header from Ramos concedes a corner, but he does better from the resulting delivery to clear behind once more.
That's the end of Alves' game. He is forced off with Montoya the man replacing him.
Alves runs into Ozil and Ronaldo surges forward. Barca get the bodies back and as Alves goes down with a knock, Adriano earns his side a throw-in.
Incredible scenes! Benzema is in acres of space from Di Maria's pass and hits the post. On the rebound, Di Maria then stabs the ball wide when the goal was gaping.
Real are deservedly effort but Barca should really do better. Ronaldo is in too much space as Benzema plays him in and the engimatic forward fires past Valdes at the near post. 1-0 to the visitors!
GOAL FOR REAL MADRID - RONALDO!
Brilliant work from Arbeloa to cut out Messi's ball into the box, which sees Madrid break as Pepe incredibly surges forward up to Barca's penalty box with Mascherano playing back to Valdes.
The hosts put together a lovely passage of play. Pedro cuts inside Marcelo, before playing in Iniesta who twists and turns before unleashing an effort not too far from finding the top corner.
Great chance for Ramos! The centre-back is inexplicably unmarked from the corner but he buries his header hide as another golden chance goes begging for the visitors.
Khedira's run is spotted by Alonso, and Adriano covers well to block the cross and concede a corner.
Khedira steps in to cut off neat interplay between Iniesta and Messi, with Barca still yet to enter their opponent's penalty box.
Marcelo sprays a ball up the field to Di Maria but it's fired with such pace that it ends up flashing out of play.
Pepe poorly controls a pass back from Khedira, and as Messi intercepts, the referee eventually awards the free-kick to Madrid, with Pepe a very lucky boy.
Alonso is felled in a hefty collision with Pedro, but after grimacing with an apparant knock to the back, he's back on his feet.
What a chance! Ronaldo's ball isn't great but it lands on the right foot on Benzema who fires well wide from just inside the penalty area.
Di Maria drives out of defence, claiming a free-kick on Busquets and in the end it's given, with replays showing a tug on the Madrid man's shirt.
Iniesta tries to cut inside Arbeloa but the defender stays very composed and intercepts precisely.
Ozil can't pick out Ronaldo and Barca regain possession, with Messi clipped by Khedira as the referee perhaps surprisingly waves play on.
Fabregas forces an unconvincing header away from Pepe, and the home fans roar after a botched clearance from Ramos.
Ronaldo nearly directs a lovely ball into the path of Benzema's run but Mascherano is positioned well enough to clear away.
Adriano times his tackle to perfection on Benzema, cutting off the striker's run and winning a throw-in for his troubles.
Madrid build a promising move but Marcelo is ignored on the left and Di Maria ends up taking a stab which sails into the fans.
Alba is played over the top of Arbeloa but Adriano's ball carries a tad too much pace and ends up travelling out before the left-back can retrieve it.
Ronaldo falls under Alves, and while the Barca right-back won a chunk of the ball, Ronaldo's protests see the decision go to Madrid.
Ronaldo looks to venture down the left but a strong challenge from Adriano dispossess the Portuguese.
Lovely early touches from Di Maria, but Ozil runs out of space as Mascherano, marshelling a three-man defence tonight, calmly plays back to Valdes.
Read Madrid get the game underway.
The atmosphere is simply astounding as we near to kick-off, with one of the most matches in World sport soon to be underway.
As the two best players in the world go head-to-head once more, Lionel Messi can be backed at 10/3 to grab the game's first goal, while his Real Madrid counterpart Cristiano Ronaldo is priced at 9/2.
Real Madrid: Casillas, Arbeloa, Pepe, Ramos, Marcelo, Khedira, Alonso, Di Maria, Ozil, Ronaldo, Benzema.
Barcelona: Valdes, Alves, Mascherano, Alba, Iniesta, Xavi, Busquets, Adriano, Messi, Fabregas, Pedro.
Here are those teams...
Good evening and welcome to live coverage of Barcelona v Real Madrid in the first El Clasico fixture of the La Liga season. Fireworks should be guaranteed at the Camp Nou tonight and the early team news I can tell you is that Lionel Messi and Cristiano Ronaldo both start. You can send me messages tonight at firstname.lastname@example.org.
Kick-off is 1850 BST.