Rossi avoided the crash at the start

Italian Marco Melandri and championship leader Loris Capirossi were both taken to the track's medical clinic after the crash, which involved six riders.

Rossi started on pole but had to work his way up from sixth on the Yamaha after a slow restart to finish 4.509 seconds clear of Nicky Hayden's Honda.

Kenny Roberts Jr was third on a KR211V, with John Hopkins fourth on a Suzuki.

Highlights: Rossi wins Catalunya MotoGP

Rossi's team-mate Colin Edwards was fifth, with Hopkins' team-mate Chris Vermeulen sixth.

It was Rossi's second straight win after his victory in Italy two weeks ago, and his third in a row in Catalunya.

I was especially worried about Marco Melandri - fortunately Dr Costa told me all three riders were conscious and were doing OK Valentino Rossi

It also moved him up to third in the overall standings after seven races, 29 points behind Hayden, who now leads with 119.

Rossi's cause was helped by the crash at the start, which eliminated several of his main rivals from the race.

"The start was difficult," said Rossi.

"Normally it is hard to concentrate, but after a crash like the one we saw today it is even more so.

"I was especially worried about the condition of Marco Melandri, who seemed to come out badly from the first-corner incident.

"Fortunately when I got back to the box Dr Costa told me all three riders were conscious and were doing OK."

It began when Spaniard Sete Gibernau's Ducati flipped, taking John Hopkins, Melandri, Dani Pedrosa, Capirossi and Randy de Puniet with him off the circuit.

Melandri was stretchered off the track, but a Honda team official said that the Italian had been conscious as he was taken to the clinic.

Gibernau, Melandri and Capirossi did not line up when the race was restarted after a half-hour delay.

Casey Stoner followed up his initial flying start by surging into the lead.

But the Australian was passed by Rossi on lap eight, and his hopes of a podium finish on the Honda ended when he slid out on the following lap.

"I made a mistake on the second start, and dropped a number of positions," said Rossi.

"From there I had a full tank and it was difficult to overtake, but once I had caught up with the first group I got faster."

Hayden tracked Rossi in the later stages of the race but he was unable to mount a serious challenge.

Catalunya MotoGP results
1. Valentino Rossi (It) Yamaha 41:31.237
2. Nicky Hayden (US) Honda 41:35.746
3. Kenny Roberts Jr (US) KR211V 41:40.411
4. John Hopkins (US) Suzuki 41:44.702
5. Colin Edwards (US) Yamaha 41:53.785
6. Chris Vermeulen (Aus) Suzuki 41:56.435
7. Makoto Tamada (Jpn) Honda 42:01.859
8. Carlos Checa (Sp) Yamaha 42:02.514
9. James Ellison (GB) Yamaha 42:30.440
10. Alex Hofmann (Ger) Ducati 42:45.299
11. Jose Luis Cardoso (Sp) Ducati 43:18.052

Standings
1 Nicky Hayden (USA) Honda 119pts
2 Loris Capirossi (Ita) Ducati 99pts
3 Valentino Rossi (Ita) Yamaha 90pts
4 Marco Melandri (Ita) Honda 89pts
5 Dani Pedrosa (Spa) Honda 86pts
6 Casey Stoner (Aus) Honda 65pts
7 Colin Edwards (USA) Yamaha 60pts
8 Toni Elias (Spa) Honda 53pts
9 Makoto Tamada (Jpn) Honda 49pts
10 Kenny Roberts (USA) Honda 44pts