Helio Castroneves benefited from a superb final pitstop to snatch Texas IndyCar victory from his Penske team-mate Ryan Briscoe, who had dominated most of the night.
Briscoe looked untouchable for the majority of the race, but found himself pipped in the closing stages for the second time in a week, as on this occasion Castroneves slipped ahead in the pits.
Ganassi's Scott Dixon took third, with Marco Andretti mounting a late charge to take fourth from pole-sitter Dario Franchitti and Danica Patrick.
The race got off to a dramatic start as Graham Rahal spun his Newman/Haas/Lanigan car and collected EJ Viso (HVM) and Milka Duno (Dreyer & Reinbold) on only the second lap.
But once that incident was cleared, an extremely long period of green flag racing ensued, allowing Briscoe to take control.
He passed Franchitti for the lead on lap 12, and steadily edged away from the rest of the Ganassi and Penske top four pack.
Helped slightly by his pursuers getting caught up trying to lap Alex Tagliani and Ed Carpenter, Briscoe was able to stretch his lead to as much as eight seconds, and lapped everyone up to seventh place by half-distance.
A debris caution on lap 151 brought the pack back onto Briscoe's tail, but he was able to stay in front until the final round of pitstops, which came under yellow after AJ Foyt IV had a suspension breakage and hit the wall.
Castroneves' crew produced a slightly quicker stop than their counterparts on Briscoe's #6 car, allowing the Brazilian to edge ahead of his team-mate coming out of the pits.
Briscoe stayed glued to Castroneves' tail throughout the final stint, but there was no way around the Brazilian, who duly clinched his second win in three races.
Dixon gradually lost touch with the Penske duo and came home third. His team-mate Franchitti had been on course for fourth until Andretti slipped ahead on the final lap as the Ganassi car ran low on fuel. Andretti had just emerged from an extremely tight late battle with his Andretti Green team-mate Danica Patrick, having earlier run as high as second as he gained speed near the end of each stint.
Dan Wheldon took seventh for Panther Racing, while Tony Kanaan made good early progress from 16th on the grid to get into the top ten, but eighth proved to be his limit tonight.
Sharp Vision Racing strategy helped Ed Carpenter recover from a mid-race slump to get up to ninth, ahead of Mario Moraes (KV) and top rookie Robert Doornbos (Newman/Haas/Lanigan).
Pos Driver Team Time 1. Helio Castroneves Penske 1h55m16.1670s 2. Ryan Briscoe Penske + 0.3904s 3. Scott Dixon Ganassi + 2.2461s 4. Marco Andretti Andretti Green + 4.3745s 5. Dario Franchitti Ganassi + 4.7695s 6. Danica Patrick Andretti Green + 5.2980s 7. Dan Wheldon Panther + 7.6203s 8. Tony Kanaan Andretti Green + 8.5009s 9. Ed Carpenter Vision + 18.7088s 10. Mario Moraes KV + 1 lap 11. Robert Doornbos Newman/Haas/Lanigan + 1 lap 12. Raphael Matos Luczo Dragon + 2 laps 13. Tomas Scheckter Dreyer & Reinbold + 2 laps 14. Alex Tagliani Conquest + 3 laps 15. Justin Wilson Coyne + 3 laps 16. Ryan Hunter-Reay Vision + 3 laps 17. Sarah Fisher Fisher + 6 laps 18. Jaques Lazier 3G + 18 laps 19. Mike Conway Dreyer & Reinbold + 43 laps Retirements: AJ Foyt IV Foyt 170 laps Hideki Mutoh Andretti Green 153 laps Graham Rahal Newman/Haas/Lanigan 1 lap Milka Duno Dreyer & Reinbold 1 lap EJ Viso HVM 1 lap