Rossi has won five out of six races this year

Honda rider Gibernau led for most of the 25 laps in Barcelona, only for Rossi to pass him on lap 23 to take his fifth win of the season on the Yamaha.

Gibernau had been seeking revenge over the world champion for the last-lap incident which cost him a win at Jerez.

Marco Melandri came out on top in a battle with Alex Barros and Nicky Hayden to take the final podium place.

"I'm very happy. It was a fantastic race," said Rossi.

"Gibernau had the best rhythm of early laps and it was very fast and I needed to be at 100% to follow him, it was quite difficult.

"I tried to go in front but I didn't have the pace.

"Then the conditions changed with the tyres and I tried to overtake and then had a fantastic last three laps to win a fantastic result."

Rossi now leads Melandri by 58 points in the title race.

"It's the beginning of the season and this advantage in the championship helps the team work in a relaxed way," the champion said.

"The season has started very well for us and we'll try to continue like this."

Gibernau had lost out to Rossi in more dramatic fashion in the first race of the season at Jerez after their bikes came together on the final lap.

He had better grip and we could do nothing about that Sete Gibernau

And the Spaniard admitted tyre wear had cost him the chance to set the record straight against his Italian rival.

"With eight laps to the end I lost too much grip and that was our race for the day," said Gibernau.

"I tried to keep the pace but I was sliding too much. He had better grip and we could do nothing about that.

"It looks like we're struggling too much. We just need to keep working to win races."

Gibernau spent a frantic opening to the race dicing for the lead with Telefonica Movistar Honda team-mate Melandri, and at one point he bumped into the back of the Italian's bike.

MOTOGP STANDINGS 1 Valentino Rossi 145 points 2 Marco Melandri 87 3 Max Biaggi 77 4 Sete Gibernau 73 5 Alex Barros 65

Barros survived a scary moment of his own when his Camel Honda made contact with Max Biaggi's Repsol Honda.

And Makoto Tamada's race was ended early when his Konica Honda slid off into the gravel on lap six while running sixth.

Gibernau maintained a gap of about half a second over Rossi as the leading pair eased away from the chasing pack.

But Gibernau had no answer when Rossi made his move down the main straight on the Gauloises Yamaha.

And the world champion backed it up with an immediate lap record to set up a fourth straight win.

Third place was up for grabs right until the end, when Melandri made Barros pay for a late mistake to join Gibernau on the podium.

In the 250cc race, Spaniard Daniel Pedrosa claimed his fourth win of the season, with Australia's Casey Stoner second and Italy's Andrea Dovizioso third.

Italy's Mattia Pasini won the 125cc race to take the championship lead from Thomas Luthi.

Catalunya GP results:
1 Valentino Rossi (It) Yamaha 43:16.487
2 Sete Gibernau (Sp) Honda at 1.094
3 Marco Melandri (It) Honda at 7.810
4 Alex Barros (Brz) Honda at 8.204
5 Nicky Hayden (US) Honda at 8.273
6 Max Biaggi (It) Honda at 12.051
7 Colin Edwards (US) Yamaha at 18.762
8 Troy Bayliss (Aus) Honda at 42.631
9 Shinya Nakano (Jpn) Kawasaki at 46.638
10 Ruben Xaus (Sp) Yamaha at 46.692
11 Carlos Checa (Sp) Ducati at 1:00.357
12 Loris Capirossi (It) Ducati at 1:03.864
13 David Checa (Sp) Yamaha at 1:03.985
14 Roberto Rolfo (It) Ducati at 1:10.258
15 Kenny Roberts Jr (US) Suzuki at 1:23.731

250cc results:
1 Daniel Pedrosa (Sp) Honda 41mins 29.428secs
2 Casey Stoner (Aus) Aprilia at 5.637secs
3 Andrea Dovizioso (It) Honda at 10.597
4 Hiroshi Aoyama (Jpn) Honda at 17.638
5 Simone Corsi (It) Aprilia at 19.499
6 Randy de Puniet (Fr) Aprilia at 33.235
7 Yuki Takahashi (Jpn) Honda at 37.408
8 Sylvain Guintoli (Fr) Aprilia at 37.530
9 Mirko Giansanti (It) Aprilia at 42.814
10 Alex Baldolini (It) Aprilia at 43.611
11 Alex Debon (Sp) Honda at 43.891
12 Roberto Locatelli (It) Aprilia at 45.800
13 Erwan Nigon (Fr) Honda at 58.190
14 Hugo Marchand (Fr) Aprilia at 1:04.356
15 Gregory Leblanc (Fr) Aprilia at 1:04.399