The Boston Athletic Association says online registration for the April 18, 2011, race began at 9 a.m. Monday.
Entrants must meet the BAA's time standards, which vary according to age and gender.
Qualifying standards for the 2011 Boston Marathon must be met on or after Sept. 20, 2009, at a marathon certified by USA Track & Field, or a foreign equivalent.
The registration fee is $130.
The field for the 2011 race is capped at 22,790.
That ceiling was reached in just two months last year, and the field is expected to fill even faster this year.
Last year, Kenya's