The league was dissolved from 1956-1961, but was restarted in 1962 with five teams. The Seibu Lions minor league affiliate joined the league in 1979, and the Tohoku Rakuten Golden Eagles did the same in 2005.
The league contains the minor league affiliates of seven Japanese professional teams (minor league homefield shown in parentheses):
Most of the Japanese minor league teams carry the same name, and use the same uniforms as their parent team, with the exception of the Orix Buffaloes (Surpass) minor league team. Saitama Seibu Lion's minor team name depends on the sponsored company, but they will use the professional team name in 2008 since the previous company's (Goodwill) naming right was void in 2007 as a result in illegal commercial movements.