This article reports the results of a questionnaire survey of a representative random sample of all the in-school Francophone adolescents of Montreal. The sample size was 4,539 and included adolescents from legally intact homes, separated/divorced homes, and homes in which a parent was decreased. Health-risk behavioral indicators were smoking (how many cigarettes a day), fastening of car seat belts, and intemperate drinking. Adolescents who lived in intact families engaged less in health-risk behavior than the other adolescents, especially those from separated/divorced families. The results for adolescents from widowed families were mixed. Several mutually complementary explanations are presented.