BOSTON -- The two women ran side-by-side at record pace for 24 miles through the streets leading into Boston.

	Margaret Okayo of Kenya celebrates her women's course record of 2:20.43.

But 25-year-old Margaret Okayo said she was not even aware that fellow Kenyan Catherine Ndereba, the world record-holder and two-time defending Boston Marathon champion, was breathing down her neck.

"I was just concentrating on my own race," the reigning New York champion said after beating Ndereba by 29 seconds and the course record by more than a minute Monday. "I was totally comfortable."

Okayo finished in 2 hours, 20 minutes, 43 seconds, tying the fourth-fastest women's marathon time in history and topping the previous Boston best of 2:21:45 set by Uta Pippig in 1994. Just five months ago, Okayo similarly shattered the 10-year-old course record in the New York Marathon.

The third-place finisher, Elfenesh Alemu of Ethiopia, was more than five minutes back at 2:26:01.

With her record-setting victory, Okayo ended Ndereba's bid to join Pippig (1994-96) and Ethiopia's Fatuma Roba ('97-99) as the third consecutive winner of three Boston titles in a row.

"There was a lot of pressure, first from the media and also from my fellow competitors. But I am very much happy and very much proud for my fellow Kenyan," said Ndereba, known as "Catherine the Great."

Ndereba still has the world record with her 2:18:47 in the 2001 Chicago Marathon, though Paula Radcliffe of Britain fell just nine seconds short in the London Marathon on Sunday.

Okayo, who has won four of her six finishes, ran in her first U.S. marathon in Chicago in 1999, where she was runner-up to Joyce Chepchumba by one second.

In addition to the Boston and New York course records, Okayo also holds the course record for the San Diego Rock 'N' Roll Marathon, which she won in 2000 and 2001.

Okayo and Ndereba appeared headed for a photo finish as they ran side by side for miles, the reigning champion just a pace behind her challenger.

But approaching Kenmore Square in Boston, at the 25-mile mark, Okayo pulled away and never looked back.

"Something was bothering my hamstring," Ndereba said. "I decided I couldn't push it anymore."

Okayo had a pained expression and appeared to vomit after she broke through the finish tape, but then she brightened as she spied one of her supporters and leapt into his arms.

Having advised Okayo on how to run Boston, Ndereba embraced the new champion near the finish line and the two women leaned on each other for several seconds.

Sun Yingjie of China led the field through 25 kilometers at a record pace, but -- as she did in two previous appearances in Boston -- she faded in the second half. By the 19-mile mark, she had dropped behind the front-runners by 32 seconds and the Kenyan duel was on.

Sun finished in fourth place, almost seven minutes behind Okayo at 2:27:26.

In 2000, Sun stayed with the top two women for 19 miles before finishing eighth in 2:31:22.

Jill Gaitenby of Northampton, Mass., was the top U.S. woman for the second year in a row, with a time of 2:38:55. She finished 13th, one spot higher than last year, but more than two minutes slower than in 2001.

"The race for me was rough from the very beginning," she said. "I think I limped for the last two miles, but I made it."