Italian Marco Melandri won a four-way battle for the MotoGP race victory in Turkey as defending champion and fellow countryman Valentino Rossi had to fight hard to finish fourth.
Melandri got the better of three other Honda riders at Istanbul as he rediscovered the form which saw him finish last season season in winning style.
The Fortuna Honda rider out-performed Australian Casey Stoner's LCR Honda on a thrilling final lap which saw Dani Pedrosa crash while in third on the Repsol Honda.
The Spaniard, the reigning 250cc world champion who had started the race in a lowly 16th, remounted to cross the line in 14th, allowing his American team-mate Nicky Hayden to claim the final spot on the podium and the series lead.
Rossi started the race 11th on the grid as he again struggled with his Camel Yamaha but the Italian came through to take fourth by the finish flag.
Hayden's third place moved him into the lead in the series on 52 points, one ahead of Italian Loris Capirossi who finished the race in sixth on the Ducati Marlboro machine.
Melandri lies third on 45 points, with Stoner on 41 and Rossi 40.
British rider James Ellison had a bad day on the Tech 3 Yamaha and finished 18th to lie 17th in the points table.
Hayden said: "To be leading the championship is something to be proud of.
"All in all I think it was a pretty good weekend, we'll run with it and put the heat on them next time."
A thrilling 250cc race win went to Japan's Hiroshi Aoyama who gave Austrian firm KTM their first GP win in the class.
But Aoyama's first win for Red Bull KTM was overshadowed by a last-lap high-speed collision between Fortuna Aprilia's Hector Barbera and Master Aspar Aprilia's Alex De Angelis, which both riders somehow survived.
As the first four riders jockeyed for position on the final lap, Barbera and De Angelis both went past Aoyama and Italian Andrea Dovizioso on the Humangest Aprilia along a fast straight.
Spaniard Barbera and De Angelis collided in the middle of the track and the San Marino rider was lucky to stay on his machine, which whipped wildly and dug the footrest into the track surface.
Aoyama and Dovizioso avoided the melee to take first and second, with Barbera finishing third and De Angelis recovering to take 12th.
Spaniard Jorge Lorenzo's bid for three straight wins in as many races in the 250cc class ended in the first corner of lap one as his Fortuna Aprilia was forced off, dropping him to second in the points table behind Dovizioso.
Welshman Chaz Davies retired his Campetella Aprilia at just over half distance and now lies 21st in the championship.
Alvaro Bautista's bid for three straight wins in the 125cc class were denied by team-mate Hector Faubel who took the victory with a pass on the final lap.
Finland's Mika Kallio's gearbox problems on his Red Bull KTM with two laps to go saw forced him out of second and meant it was a Master Aspar Aprilia one-two-three as Sergio Gadea also made it three Spaniards on the podium.
Bautista heads the standings on 70 points ahead of Faubel on 45 and Gadea with 41.
British teenager Bradley Smith was on course for his best finish of the season when he crashed.
The Repsol Honda rider was 22nd when he slid off and is still looking for his first world championship point of the season after three races.
