OBJECTIVE: To determine the incidence, nature, demographics, severity, and hospital charges associated with inpatient treatment of firearm-related injuries. DESIGN: A retrospective, 1-year, population-based study of firearm-related hospitalizations based on the 1991 California Hospital Discharge Abstract Data Tapes. SETTING: California acute care hospitals that reported firearm-related discharges. PATIENTS: A total of 9562 patients discharged with firearm-related injuries. MAIN OUTCOME MEASURES: Per capita hospital discharge rates, according to age, race, and sex. RESULTS: A total of 9562 firearm-injured persons were discharged from California hospitals in 1991, representing a rate of 32 discharges per 100 000 population. Males aged 15 to 24 years accounted for 72% of the hospitalizations. For all causes of firearm-related injury, the highest age- and race-specific discharge rate was 439 per 100,000 for black persons aged 15 to 24 years. The highest county discharge rate was 55 per 100,000 for Los Angeles County. Statewide, there were 1.8 hospital discharges per firearm-related fatality (both in the hospital and in the community). Assaults accounted for 74% of cases. Among black males aged 15 to 24 years, assaults accounted for 598 discharges per 100 000 population. Hospital charges for 9193 patients exceeded $164 million; mean and median charges per patient discharged were $17,888 and $8535, respectively. Publicly financed health insurance programs sponsored 56% of patients; 25% had private insurance, and 19% were uninsured. Fifty-three percent of the discharges occurred at 13 of the 371 hospitals that discharged patients with firearm-related injuries. CONCLUSIONS: Firearm-related violence is a major cause of hospitalization of young urban black males and represents a significant cost to publicly financed health care. The impact on individual hospitals is highly disproportionate. While hospital discharge data can be used for population-based surveillance of firearm-related trauma, there is need for improvement in local, state, and national surveillance of these injuries.