Takuma Sato claimed a dramatic victory in the 2017 Indianapolis 500, while Fernando Alonso retired with an apparent engine problem while in contention to win with 21 laps remaining.
IndyCar's premier race boiled down to an 11-lap dash to the flag after an incident-packed event that featured 11 caution periods.
Chip Ganassi Racing driver Max Chilton, who started 15th, had moved into contention among the leaders by staying out when the third caution of the race was thrown on lap 81 of the 200 because of debris shed by Marco Andretti's car.
Chilton then got on level terms with the leaders strategically when he made a green-flag pitstop at the end of lap 166, moments before team-mate Charlie Kimball's Honda engine let go.
At the final restart, which followed a caution for a five-car crash triggered by Oriol Servia spinning into James Davison and led to Will Power, James Hinchcliffe and Josef Newgarden getting caught up in a chain reaction, Chilton led from Sato, Ed Jones and Helio Castroneves.
Castroneves was the man on the move, going around the outside of Jones at Turn 3 on lap 190 and then, with nine laps remaining, performing another high pass on Sato to take second.
With seven laps to go, Castroneves went around the outside of Chilton at Turn 3 to take the lead and looked set to claim a record-equalling fourth Indy 500 win.
But Sato followed Castroneves past Chilton on the main straight to run second and closed on the leading Penske driver.
The key move happened with five laps remaining, as Sato drafted past on the main straight to take a lead he would never lose despite Castroneves having a look around the outside of Turn 1 on the penultimate lap.
After that, Sato was clear and took victory in his Andretti Autosport Dallara-Honda by 0.2011 seconds from Castroneves.
The result made Sato the first Japanese driver to win the Indy 500.
Dale Coyne Racing rookie Ed Jones was third after passing Chilton late on, with Tony Kanaan, who led the race early on, fifth ahead of Juan Pablo Montoya.
Alonso had several stints in the lead of the race, and at the time of the failure was working his way through several drivers who had moved ahead thanks to strategy and looked a serious threat to win.
RESULTS - 200 LAPS:
||Dale Coyne Racing
||Chip Ganassi Racing
||Chip Ganassi Racing
||Juan Pablo Montoya
||A.J. Foyt Enterprises