To describe the epidemiology of injuries in the Australian Football League (AFL) over four seasons. An injury was defined as "any physical or medical condition that caused a player to miss a match in the regular season." The rationale for this definition was to eliminate a previously noted tendency of team recorders to interpret injury definitions subjectively. Administrative records of injury payments to players who did not play matches determined the occurrence of an injury. The seasonal incidence of new injuries was 39 per club (of 40 players) per season (of 22 matches). The match injury incidence for AFL games was 25.7 injuries per 1000 player hours. The injury prevalence (percentage of players missing through injury in an average week) was 16%. The recurrence rate of injuries was 17%. The most common and prevalent injury was hamstring strain (six injuries per club per season, resulting in 21 missed matches per club per season), followed in prevalence by anterior cruciate ligament and groin injuries. The injury definition of this study does not produce incidence rates that are complete for all minor injuries. However, the determination of an injury is made by a single entity in exactly the same manner for all teams, which overcomes a significant methodological flaw present in other multiteam injury surveillance systems.