We studied the incidence of injury in girl's varsity basketball to characterize injury demographics in high school athletics. We defined a reportable injury as one that occurred during organized practice or competition, resulted in either missed practice or game time, required physician consultation, or involved the head or face. We prospectively evaluated the athletes on team rosters during the 1993 to 1994 season from 100 randomly selected Class 4A and 5A Texas public high schools that employed full-time certified athletic trainers. The 890 student athletes from 80 schools ranged in age from 14 to 18 years. Four hundred thirty-six injuries were reported for a rate of 0.49 per athlete per season. Injury risk, calculated on the basis of exposure time, was 0.4% per hour per athlete. Although game time accounted for only 12.5% of exposure time, it represented one half of the total injuries. Sprains and strains (56%) were the most common injuries, followed by contusions (15%) and dental injuries (14%). Injuries to the ankle (31%) and knee (19%) were by far the most common. There were 34 severe injuries defined as requiring surgery or hospitalization, for a rate of 0.038 per athlete per season. Knee injuries were by far the most likely to require surgeries, and ACL injuries accounted for 69% of the severe knee injuries.