Purpose: To assess differences in health-related behaviors between athletes and nonathletes. Methods: In Grades 9-12 in seven high schools during the 1991-1992 academic year, 7179 (82%) students were asked to complete a survey with six categories of health-related behaviors associated with adolescent morbidity and mortality. Of the 6849 students who completed the survey, 4036 (56%) were classified as athletes. Analyses of differences were controlled for age, race, and gender. Results: Athletes and nonathletes differed in specific health-risk behaviors. Nonathletes were more likely than athletes ever to have smoked cigarettes (15% vs. 10%) or used marijuana (24% vs, 23%), and fewer ate breakfast daily (34% vs. 45%), never added sale to food (18% vs. 22%), consumed calcium (56% vs. 64%), or consumed fruit or vegetables (40% vs. 47%) daily. More nonathletes reported frequent feelings of hopelessness (15% vs. 10%) and rarely or never using seatbelts (24% vs. 20%), but more athletes reported exceeding the speed limit by 10 mph (39% vs. 35%) and riding bicycles (40% vs. 28%) and/or motorcycles (13% vs. 8%) without helmets. These differences were statistically significant. Conclusions: Because of their behaviors, adolescent athletes put themselves at significant risk for accidental injuries. However, athletes appear less likely to smoke cigarettes or marijuana, more likely to engage in healthy dietary behaviors, and less likely to feel bored or hopeless. (C) Society for Adolescent Medicine, 1998.