The 96th Indianapolis 500 blasted into action on Sunday on a steaming hot day in America's Midwest after an emotional tribute to last year's winner Dan Wheldon.
A massive crowd, estimated at around a quarter of a million, let out a mighty roar when the green flag was dropped and the 33 cars sped away for the first of 200 laps on the sprawling oval track.
Australian Ryan Briscoe started from pole position after setting the fastest time in qualifying and was joined on the front row of the grid by Canada's James Hinchcliffe and American Ryan Hunter-Reay.
Marco Andretti, bidding to end his family's apparent curse in the race, was on the second row alongside Australia's Will Power, the current IndyCar series leader, and three-time Indy 500 winner Helio Castroneves of Brazil.
The field included eight rookies, three women and two ex-Formula One drivers, Brazilian Rubens Barrichello and Jean Alesi of France, and drivers from 11 different countries, the United States, Canada, Australia, New Zealand, Japan, Mexico, France, Spain, Venezuela, Brazil and Switzerland.
There were three former champions in Castroneves, bidding to become just the fourth four-time winner, Briton Dario Franchitti and New Zealand's Scott Dixon.
This year's race is one of the most open and unpredictable in years and was shaping up as grueling test for both the drivers and their cars with temperatures forecast to reach 95 degrees Fahrenheit (35 degrees Celsius).
Part of the race's enduring appeal is that it is steeped in tradition and once again the race was preceded by the singing of "Back Home in Indiana Again" and the eventual winner was expected to follow custom by kissing the bricks and slugging milk.
Before Sunday's race, the sport paused to remember Wheldon, the popular Englishman who was killed in a horrific crash in Las Vegas in October.
His tragic death continues to cast a dark pall over the sport and has added a somber sense to this year's race.
The car he won in 12 months ago, was driven on a lap of honour, serving both as a tribute to him and a stark reminder of the dangers the drivers face when hurtling around the track at speeds of 220 mph (350 km/h).
(Editing by Gene Cherry)