The Association of Tennis Professionals (ATP) Tour is the elite professional tennis circuit organised by the ATP. The 1999 ATP Tour calendar comprises the Grand Slam tournaments, supervised by the International Tennis Federation (ITF), the ATP Super 9, the ATP Championship Series, the ATP World Series, the ATP World Team Cup, the ATP Tour World Championships and the Grand Slam Cup (organised by the ITF). Also included in the 1999 calendar are the Davis Cup and the Hopman Cup, which do not distribute ranking points, and are both organised by the ITF.
In April 1999 ATP signed a $1.2 billion 10-year-deal with the sports marketing agency ISL Worldwide to promote the sport. The deal gave ISL the commercial rights for the Super-9 tournaments as well as the ATP World Championship. The ATP also introduced a simplified ranking system and made participation in the Super-9 events mandatory for top players.