Cheruiyot, who also won in 2003 and set the course record last year, outkicked countryman James Kwambai as they headed into Kenmore Square with a mile to go. And the defending champion kept his feet under him as he crossed the finish line - something he had a bit of a problem with when he won in Chicago last fall.

This time, Cheruiyot held his arms to the side and blew a kiss to the crowd as he stepped over the slip-proof line 20 seconds ahead of Kwambai. Kenya won its 15th men's title in the last 17 years and swept the top four spots on the men's side.

Grigoryeva, who set the course record in Los Angeles last year, veered to the stands to grab a Russian flag just before crossing the finish line to win by 40 seconds and claim her $100,000 first prize.

The weather was milder than forecasters had feared - 52 degrees with a moderate rain at the start- and the sun even came out halfway through. But winds picked up as the runners turned onto Beacon Street in Cleveland Circle for the last, long homestretch to Copley Square.

The leading women ran in a pack of seven for the first half of the race before several, including defending champion Rita Jeptoo and top American Deena Kastor, began to fall behind. Kastor slowed just past the midpoint, and Jeptoo at the 17-mile mark, heading into the Newton hills.

Grigoryeva, Latvia's Jelena Prokopcuka and Mexico's Madai Perez ran shoulder to shoulder from there until Perez and then Prokopcuka fell back as they crossed the Massachusetts Turnpike and headed into Kenmore Square.

The two-time defending champion of the New York City Marathon, Prokopcuka was second to Jeptoo in Boston last year in the closest finish - 10 seconds - in the history of the women's race. This year's race wasn't as close but her finish was the same; Perez was third, another 18 seconds back.

Cheruiyot won in 2:07:14 last year and then went on to win Chicago. But what seemed to be a runaway turned scary when he slipped on the finish line and banged his head on the pavement as he raised his hands to celebrate breaking the tape.

Although at first it wasn't even clear he made it to the end, his torso bounced across the line as he fell and hit his head. Since then, he's had trouble sleeping, blurry vision and back problems. During a training race three weeks ago he went back to the hospital because of headaches.

Back in Boston, though, Cheruiyot managed to stay upright on the slick and puddled pavement.

A total of 23,903 runners registered for the race, with 2,449 choosing not to pick up their bib numbers over the weekend. More no-shows were expected at the start, and organizers worked through the night to line up shelters for those dropping out along the course.

Pumps have been stationed at low-lying areas in case of flooding. Ponchos were provided for workers assigned outdoors. Runners were warned by e-mail to wear appropriate clothing.

Near the start in Hopkinton, the usual carnival atmosphere was subdued. The town green was nearly empty less than two hours before start time, with few hot dog stands and no lines at the portable restrooms. A vendor who ran out of ponchos Sunday was selling trash bags for $1 apiece.

One reason may be the new starting time — 10 a.m. for the main field, after more than 100 years of noon starts — that was adopted in part, ironically, because of a few years of afternoon heat. The earlier start also allowed cities and towns along the route to have their roads back sooner.

Many runners started in jackets and gloves but ditched them as they warmed up over the day. By the time the lead pack of seven women reached Natick after about 10 miles, the rain had stopped and the wind had died.

Jeptoo struggled to remove her overshirt as they went through Wellesley, running a few yards with it stuck on her head. Kastor ditched her sleeves as well.

Despite a disappointing finish, Kastor earned the U.S. title and a bonus of $25,000. She has said she does not want to run the marathon at the worlds in Osaka, Japan.

Cheruiyot is in line for a nice little bonus of his own: He all but wrapped up a $500,000 bonuses from the World Marathon Majors circuit; Jelena Prokopcuka leads the women's points race with 55 points (25 points are awarded for a win, 15 for second).