Marathon stride-by-stride webcast, continued

12:55 p.m.: Vincent Kipsos has regained the lead in the men's race; in the women's race, Svetlana Zakharova of Russia has caught up to Marla Runyan of Oregon, Lyubov Denisova of Russia, and Margaret Okayo of Kenya. The four women are neck-and-neck. In the wheelchair race, Ernst Van Dyk of South Africa and Edith Hunkeler of Switzerland are still in the lead.

12:50 p.m.: The men's pack is catching up to and passing Vincent Kipsos in the men's race. Lyubov Denisova of the Russian Federation is slightly leading the woman's race, but Margaret Okayo of Kenya and Marla Runyan of Oregon are close behind. The woman are on a 2:23 pace.

12:45 p.m.: Lyubov Denisova of the Russian Federation is slightly leading the women's race, butMargaret Okayo of Kenya and Marla Runyan of Oregon are close behind.

12:40 p.m.: Lyubov Denisova, 31, of the Russian Federation has moved into the lead of the women's race and Marla Runyan, 34, of Oregon, who is legally blind, has moved into second place. Okayo has fallen back to third.

12:30 p.m.: There has been an accident in the wheelchair race behind Ernst Van Dyk involving three chairs. Channel 4 is reporting that a child was hit by one of the chairs. Runners Vincent Kipsos and Margaret Okayo, both of Kenya, and wheelchair racers Ernst Van Dyk of South Africa and Edith Hunkeler of Switzerland are all still leading their respective races.

12:20 p.m.: Vincent Kipsos of Kenya has run each of the course's first three miles in fewer than 5 minutes. Ernst Van Dyk of South Africa is still leading the men's wheelchair race, while Edith Hunkeler is ahead among the female wheelchair racers. Both Van Dyk and Hunkeler are defending champs in Boston.

12:15 p.m.: Boston defending champion Margaret Margaret Okayo, 26, of Kenya is leading the women's race. She set her personal best of 2:20:43 in Boston last year.

12:10 p.m.: Kipsos ran the first mile in 4:44. He has done 3K in 9 minutes.

12:03 p.m.: Vincent Kipsos, 33, of Kenya is in the lead in the very early going. His personal best is 2:06:52, set in Berlin last year.

Noon: More than 20,000 runners have left the starting line in Hopkinton for Boston.

11:55 a.m. Men's wheelchair racer Ernst Van Dyk is well ahead of the field at the four-mile mark. Meanwhile, 20,000 runners are at the starting line in Hopkinton.

11:45 a.m. The starting gun sounded and hundreds of wheelchair racers just left the starting line in Hopkinton. The runners will follow them at noon.

11:35 a.m. The wheelchair racers are lining up at the starting line in Hopkinton for the start of the Marathon. The runners will follow them at noon.

11 a.m. The athletes began gathering in Hopkinton early this morning. Most of the field of more than 20,000 are at Hopkinton High School, which serves as an Athletes' Village. They are warming up, resting, taking fluids and preparing themselves for the trek to come. The weather today is sunny, with temperatures about 60 degrees.