Zlatan Ibrahimovic's superb second-half volley was enough to give Barcelona victory over fierce rivals Real Madrid in the Primera Division's first 'El Clasico' of the season at the Nou Camp and move the Catalans back to the top of the table.
Ibrahimovic replaced Thierry Henry early in the second half and fired Barca in front less than five minutes later as he volleyed home Dani Alves' cross.
Barcelona were reduced to 10 men with almost half an hour left, when Sergio Busquets was sent off for a second bookable offence.
But Madrid, who had earlier missed a fantastic chance to take the lead when the unmarked Cristiano Ronaldo shot straight at Victor Valdes with only the Barca keeper to beat, failed to take advantage and themselves had Lassana Diarra dismissed late on.
Ronaldo went off with 25 minutes left and Barca should have made things easier with two minutes to go, when Lionel Messi found himself alone with only Iker Casillas to beat, but the winger shot straight at the Madrid keeper, who deflected the ball over with his feet.
Barca looked the more fluid of the two sides early on, but Madrid proved to be just as dangerous on the break.
Marcelo and Xavi both blasted over the bar in the opening 10 minutes as both sides began brightly.
Casillas had to be alert to gather Thierry Henry's cross after a trademark Messi run and the Madrid keeper also intercepted well moments later as Iniesta tried to set up Xavi.
Barca were edging it on possession and play, but Madrid had the best chance of the half after 19 minutes.
It fell to Ronaldo and the former Manchester United forward should have scored after he was brilliantly set up by Kaka, but his shot was too close to Valdes and the Barca keeper made a smart save.
With the score still goalless, Henry was replaced by Ibrahimovic six minutes into the second half and he smashed home Alves' looping cross with a thumping left-footed volley at the far post which gave Casillas no chance soon after.
Barca's joy turned somewhat sour six minutes later, though, when Busquets was shown the red card for a cynical handball.
Raul came on as Pellegrini rolled the dice once more in an attempt to make the most of his side's numerical advantage.
But Barca still looked dangerous on the break and Eric Abidal shot just wide of the post with 14 minutes left. And Guardiola's side should have made sure of the points with two minutes left, but Messi shot straight at Casillas.