BOSTON — The long road to the 2016 Boston Marathon is underway.

Registration for next April’s 120th running of the race opened Monday. The Boston Athletic Association, which organizes the 26.2-mile event, is using the same rolling entry procedure it’s employed for the past three years, allowing the fastest gender and age-group qualifiers to register first.

Athletes whose qualifying times are 20 minutes or faster than their standard get first dibs for April 18, 2016. If there’s still room, those who ran 10 minutes or faster than their standards can register Wednesday, and those who ran five minutes faster can do so Friday.

Organizers say registration will close for the week on Saturday night, and will reopen Sept. 21-23 if the field size of 30,000 entrants hasn’t been reached.