Although medical practitioners are aware of the violence-related mortality among American youths, the literature contains relatively little information regarding violence-related morbidity or medically oriented approaches to preventing violence. To determine the extent of violence among youth, 191 students having school-based physical examinations at one Boston high school during the 1982-83 school year were surveyed. Fifty percent of the males experienced at least one pushing or shoving fight per year, and by 16 years of age, 25 percent had been threatened with a knife or gun. The frequency of these occurrences led to the systematic introduction of violence-prevention counseling in the routine health care of adolescents in this community. This counseling has sometimes resulted in behavioral change. Case examples, table, and 6 references. (Author abstract modified)