It formerly included 7 teams, which quickly transformed into 6 due to the disbandment of once famous ballclub Sanyo Crowns.
The initial complement of teams:[1] The Sanyo Crowns were dissolved after the 1952 season.
The Shochiku Robins merged with the Taiyo Whales in 1953, but the Kintetsu Pearls' farm team joined the league that year, keeping the number of teams at six.
Until 2002, teams played each other 18 times per year (9 home and 9 away) giving a 90-game season.
In 2005, the split-season system was abolished and teams played each other 22 times each (11 home, 11 away) giving an 88-game season.
Prior to 2013 only games hosted by a team whose first team belongs to the Pacific League (Orix and SoftBank) included the designated hitter system (DH system).
Since 2013 games hosted by Hanshin also used the DH system and Hiroshima followed suit in 2015.