EMASS has two leagues and players can participate in one or both of them. The number of teams in each league is subject to seasonal changes depending upon the number of players registered.

• The Saturday league is divided into two divisions. In 2010, the American Division will have 6 teams and the National Division will have 10 teams. Games are played on Saturday mornings. Both Saturday divisions have paid umpires and playoffs.
  
• In 2010 the Atlantic Division will have 10 teams. Games are played in Wayland on Tuesday and/or Thursday mornings. Umpires will be provided by the newly formed "EUA" (EMASS Umpires Association).

The American Division in the Saturday league is the most competitive, as it has a higher percentage of younger and highly skilled players than either the National Division or the Atlantic Division (in which most players are retired).

In 2008, EMASS opened its doors to 50-54 year olds who would like to join the American Division. In 2009, EMASS allowed 50-54 year olds to play in the National Division if they did not qualify for the American Division.

The weekend season starts the first week in May and ends the last week in August, while the weekday division continues to play regular season games through September.

For those who want to play even more - there are tournaments, informal pick-up games, and a fall weekend league.

EMASS is led by a commissioner and a 12-member board of directors, all of whom are elected by the players.