Ethiopian Lelisa Desisa will bid for his third Boston Marathon title on Monday against a clutch of fast East African competitors, including two other previous winners from Kenya.
Most top U.S. marathoners are sitting Boston out after February's Olympic trials, but Kenyan and Ethiopian officials have yet to pick their teams for the Rio Games in August and will consider the Boston results.
Known as a tactical racer with a proven sprint finish, Desisa posted a personal best of 2:04:45 in Dubai in 2013. He won Boston in 2:09:17 last year and also claimed victory in 2013, the year bombs ripped through the crowd at the finish line.
Fellow Ethiopian Lemi Berhanu Hayle, who notched a personal best of 2:04:33 in Dubai in January, has a similarly strong record, having run just five marathons and won three.
Kenya's Geoffrey Mutai enters the race with the fastest personal time of 2:03:02, a course record he set with his 2011 Boston win. Kenyan Wesley Korirm whose personal best is 2:06:13, is returning for a fourth time after having won in 2012.
Meb Keflezighi, who became the first American to win Boston in more than three decades when he scored an emotional victory in 2014 on the anniversary of the bombings, said he would sit Boston out to prepare for the Olympic marathon.
On the women's side, Kenyan Caroline Rotich will defend last year's crown but will face pressure from Ethiopia's Tiki Gelana, who won gold at the 2012 Olympics.
American Neely Spence Gracey marks her marathon debut in Boston with personal connections. She was born 26 years ago on race day as her father, Olympian Steve Spence, ran the course.
The men and women's winners will receive $150,000. Some 30,000 people plan to participate in the race's 120th running.