KAILUA, KONA, Hawai'i — Australia's Craig Alexander rallied yesterday to win the Ironman World Championship.

The 35-year-old triathlete from Sydney completed the 140.6-mile endurance test in 8 hours, 17 minutes, 45 seconds.

Alexander, second last year in his first Hawai'i Ironman, was 11th at the end of the 112-mile bicycle ride. But he moved up after run leaders Torbjorn Sindballe of Denmark and Normann Stadler of Germany faded. At the 18-mile mark, Alexander took the lead from Eneko Llanos of Spain, who finished second in 8:20:50.

"I can't believe it. It was a hard race," Alexander said.

Britain's Chrissie Wellington won her second consecutive women's title, finishing in 9:06:23. She overcame a flat tire that cost her 10 minutes on the bike ride.

She had a 5-minute lead when her tire went flat. Rebekah Keat of Australia came to the rescue with a spare canister of air, and Wellington quickly regained the lead.

"That was the hardest thing I've ever done," Wellington said. "It didn't go exactly to plan. I had a good swim and felt strong in the first phases of the bike."

She thanked Keat, saying, "She's a legend."

Nina Kraft of Germany returned to the race after a two-year suspension for failing a drug test. She was the first woman to finish in 2004, but later was stripped of her title.

The competitors were challenged by gusty cross wind and heat during the ride through barren lava fields.

Defending champion Chris McCormack of Australia dropped out during the bike ride, about four hours into the race, due to a mechanical problem. He later said he had been told it would take 20 minutes to fix a snapped cable.

A total of 1,808 triathletes began the 30th anniversary race, often called the most challenging endurance test in the world.

The professionals started the swim at 6:45 a.m., 15 minutes ahead of the age-group competitors. Two Navy SEALS started the swim by parachuting into the water.

The competitors ranged in age from 18-year-olds Tyler Foster and Ariel Henbest of the host city of Kailua, Kona to 79-year-old Loren Leonard of Hawthhorne, Calif. Seventy-two-year-old Harriet Anderson of San Carlos, Calif., was the oldest female competitor.