The study focused on interpersonal assaultive injury, excluding sexual assault, child abuse, and self-inflicted injuries. Relevant injuries composed 75 percent of all admitted intentional injuries and involved 671 patients. The intentionally injured were compared to the catchment area population and to the remaining admitted hospital population by age, sex, and race. Medical records of intentionally injured adolescents (133) were reviewed and compared to a sample of adolescent homicide victims regarding the circumstance of the event and the relationship of victim to assailant. Relevant findings are that in the area served by this hospital, male adolescents are at relatively high risk for nonfatal intentional injury; among adolescents, the majority of these intentional injuries are the result of interpersonal conflicts between acquaintances; a prevalence of missing data in the medical records of older male adolescents is symptomatic of the lack of attention that has been paid to understanding and preventing intentional injury among adolescents. The study concludes that more area- specific and hospital-based studies of intentional injury are needed as a guide to such preventive efforts; and medical personnel who provide acute care to victims of intentional injury are an important resource for this research and prevention effort. 5 tables and 28 references