The Greek Basket League (GBL), often also referred to as the Greek A1 Basketball League, or Greek Basketball Championship (originally called Panhellenic Basketball Championship), and also known as the Stoiximan Basket League for sponsorship reasons, is the first tier level professional basketball league in Greece. It is run by HEBA (), under the legal authority of the Hellenic Basketball Federation (E.O.K.). It is the highest-tier level of the Greek league system. The GBL plays under FIBA rules and currently consists of 13 teams, with the lowest-placed team relegated to the A2 Basket League and replaced by the winner of the play-offs of that tier. It runs from October to June, with teams playing 22 games each during the regular season, and the top 8 teams then competing in the playoffs. The first official Greek Basketball Championship was held in the 1927–28 season. The league held a competition in which the teams of the league played under a format with a nationwide schedule, for the first time, in the 1963–64 season. The league first held a playoff round in the 1986–87 season. The league first allowed foreign (non-Greek) players, in the 1988–89 season. The league became a fully professional competition in the 1992–93 season. The league has always been ranked as one of the top 3-5 level national domestic leagues in European basketball, since league rankings began. For further information, see historical European national basketball league rankings, and European national basketball league rankings. History Basketball first came to Greece in the year 1924. The first Greek basketball championship took place in the 1927–28 season, the first fully organized Greek basketball championship began. The league was originally organized by the Hellenic Amateur Athletic Association (SEGAS). There have been four different official championship eras. The first era was the Panhellenic Championship (Πανελλήνιο Πρωτάθλημα), which lasted from the 1927–28 to 1962–63 seasons, when the champions of every regional district played each other to decide the Greek Champion. The second era started in the 1963–64 season, when the A National Category (Α' Εθνική Κατηγορία), or Alpha National Category was founded. In 1969, the Hellenic Basketball Federation (E.O.K.) took over the duties of overseeing the competition, and did so until the year 1992. The third era of the championship existed between the 1986–87 and 1991–92 seasons, when the first division A1 National Category (Α1 Εθνική Κατηγορία), with a regular season and playoffs, and the second division