Los Blancos coach Jose Mourinho will be looking for his side to gain some revenge, while having the added incentive of being the holders of the Spanish Cup.
What happens next is anybody's guess! Stay tuned for live coverage of the world's biggest club game.
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00min: Here we go then! The referee blows his whistle and Barcelona get us underway. We've just been shown video clips of Mourinho and Guardiola having the briefest of handshakes - who will be celebrating at the end?
01min: No early goal on this occasion. Barca have the possession but it is wasted. The Bernabeu seems strangely quiet.
03min: Barca playing the pressing game yet again, harrying the Madrid players into committing mistakes. No goalscoring chances as of yet but Barca look the more likely to create.
04min: Who had four minutes in the sweepstake for the first time Lionel Messi gets a crunching tackle come his way?! Pepe tries his best, but the little Argentine wriggles free.
05min: Now the Madrid fans are making some noise. However, they are jeering Barca's ability to keep possession.
06min: Cesc Fabregas ALMOST gets the first goalscoring chance. Iniesta controls the ball which drops out of the sky and plays a smart reverse pass. However, it is slightly over-hit and Iker Casillas collects.
08min: Cristiano Ronaldo finally introduces himself to proceedings, albeit in a defensive capacity. The Portuguese robs Gerard Pique but Gonzalo Higuain is offside and the move breaks down.
10min: It is all rather scrappy at the moment. Even the likes of Xavi and Iniesta are being careless in possession.
11min: GOAL! MADRID 1-0 BARCA - RONALDO The winger collects possession from Pepe. He then proceeds into area before dropping past Gerard Pique and shooting through Pinto's legs from a narrow angle. Game on!
14min: First shot for Barca. Iniesta cuts inside but his effort is tipped wide by Casillas.
16min: A real let off for the home team. Alex Sanchez loops a header over Casillas, who can only stand and watch as the ball cannons off the cross bar and is cleared to safety.
17min: And there it is the first booking to Madrid's Pepe for a foul on Sergio Busquets.
19min: The referee is surrounded by players from both teams following a clash between Pique and Pepe. The former is booked for his troubles.
21min: Ronaldo is almost in again there but Pinto races out of his goal to clear Lassana Diarra's through pass. Another warning for Barca.
23min: Barca are playing some neat stuff, but it is lacking in penetration. Uncharacteristically the final ball is nowhere to be seen.
25min: Big chance wasted by Ronaldo. He takes possession of Dani Alves but his square pass is cut out by Abidal. Up the other end, Messi's low drive is turned wide by Casillas. Finally, the game is livening up!
27min: Barca are almost in again there, but Iniesta's cross is lacking in power and Sergio Ramos retreats to clear ahead of the waiting Messi.
29min: Another golden chance for Barca. Xavi finds Alexis Sanchez, who in turn finds Iniesta. With the goal at his mercy, an off-balance Iniesta fires horribly wide from six yards out.
31min: Pepe has spent more time on the floor than playing football in this match. The defender is tripped by Sanchez and then proceeds to writhe around in 'agony'.
34min: Guardiola, 41 today, looks rather glum on the sidelines. His side should be at least level but they continue to spurn chances.
36min: There is more joy for Ronaldo in this tie should he want it. Playing on the left, Ronaldo is often in acres of space because of Alves's tendancy to attack.
38min: Madrid are defending well but are being wasteful in possession. The ball keeps coming back at them. Can they hold out?!
39min: Bad call from the linesman. Sanchez is in on goal following a delicate through ball from Xavi. However, the Chile international is flagged offside with only Casillas to beat. Madrid defenders Ramos and Fabio Coentrao were clearly playing him onside there.
44min: Madrid's defensive work has to be applauded. Time and again Xavi and Iniesta have strived for the killer ball but on each occasion there route has been blocked by a white shirt.
HALF-TIME One minute of stoppage time comes and goes without any incident and the referee calls time on the opening half. At times it has looked like a training match - Madrid's defence versus Barca's attack. Nevertheless, it is Los Blancos who lead 1-0 through Cristiano Ronaldo's low strike.
Half-time discussion: Why does Lassana Diarra not feature for Madrid more often? The French midfielder is constantly on the case of the Barca midfielders, winning possession and playing the simple pass. Would he not be worth a regular role in the Madrid starting lineup?
Second half underway: The players are back on the pitch and we are off and running again. No changes from either manager.
46min: Positive stuff from Barca as Fabregas skips past Pepe but his cross his cleared by Ramos. Surely Madrid cannot hold out for much longer, can they?
48min: GOAL - MADRID 1-1 BARCA - PUYOL. There we told you! Pepe falls asleep and captain Carlos Puyol ghosts in to power Xavi's corner past Casillas with a diving header.
50min: Madrid's Ramos takes his frustration at the equaliser out on Sanchez by swiping away the attacker's legs. He is rightly booked and is now on tight-rope.
52min: Madrid are wobbling at the moment and are in real danger of conceding a second. They are playing very, very deep. Perhaps Mourinho needs to make a change?
54min: Barca strike the woodwork again! Fabregas chips through to Iniesta, whose volley hits the upright via a deflection of Madrid defender Ramos. Moments later, Busquets gets himself cautioned.
57min: Now it is Madrid's turn to hit the post! Altintop's cross is met by Karim Benzema (yes, he is playing!) at the back post. However, the Frenchman's downward effort clips the foot of the post and bounces wide.
59min: Coentrao has his name taken by the referee for a late lunge on Messi.
61min: Strangely, Madrid fans jeer the own goalkeeper after Casillas's clearance goes straight out for a goal kick. Barca are back in possession, which infuriates the locals further.
63min: Yet again Pepe is rolling around on the floor, claiming to have been struck by Fabregas. Replays show the former Arsenal man made no contact with Pepe's face! Embarrassing actions.
65min: Mourinho blinks first and introduces Mesut Ozil and Jose Callejon into the action in place of Diarra and Higuain. Attacking moves from Mr Mourinho.
67min: Callejon has yet to touch the ball but he does have a yellow card to his name! The young Spaniard brings down Messi who was in full flight. While on the floor, Pepe decides to stamp on Messi's hand for no particular reason. How is he still on the pitch?
69min: Should be 2-1 win to Barca. Xavi whips in a great free-kick but an unmarked Busquets heads over from six yards out.
73min: The players appear to be taking a breather for a few moments. The game has been reduced to walking pace, although Barca are still in control.
75min: Has Lionel Messi ever been more ineffective in an El Clasico? The Argentine's touch has deserted him on numerous occasions tonight. Now preparing to eat our words...
76min: GOAL! MADRID 1-2 BARCA - ABIDAL. And there we are chewing away! Messi flicks a great ball over the top of the Madrid defence for full-back Eric Abidal, who takes one touch before poking the ball beyond Casillas. You cannot keep the Ballon d'Or winner down (despite Pepe's best efforts!)
79min: Madrid's response is positive, with Ronaldo firing across the six yard box for Callejon, who is unable to get his shot in. Mourinho makes a smart move and replaces Pepe with reported Liverpool transfer target Esteban Granero.
80min: Callejon does his best Roberto Mancini impression by waving an imaginary card for a challenge committed on him by Dani Alves. A foul is given, despite Alves clearly winning the ball.
81min: Guardiola makes his first change of the evening. Sanchez off, Adriano on.
83min: Madrid are trying to carve an opening but the route is blocked by a stubborn Barca defence. Will it be the same old story for Mourinho and his team?
86min: Another substitution for Barca. Young Spanish midfielder Thiago takes the place of Xavi.
87min: Messi takes another hammering, this time courtesy of Ricardo Carvalho who takes him down from behind. Blatant foul and deserved yellow card.
88min: Final change for Barca sees Fabregas leave the pitch to jeers from the home faithful. Cuenca enters the action for the final few minutes.
90min: The fourth official informs everybody that there is three minutes of stoppage time. Can Madrid salvage something from the tie? They need the ball first, which is proving a problem at the moment.
90+2min: Barca are keeping possession for fun at the moment. Madrid are resorting to lunging challenges and in truth, Carvalho is lucky to still be on the pitch.
FULL-TIME That's it, all over. Barca take a 2-1 lead back to the Nou Camp and you would have to fancy Guardiola's side to complete the job and advance to semi-finals next Wednesday.