This study examined the psychosocial and behavioral correlates of seat-belt use among 1,728 10th-graders in four Northern California high schools. Parent and friend seat-belt use patterns were most highly correlated with student seat-belt use (r = 0.66 and r = 0.61, respectively) and together accounted for 46% of the variation in use. These relationships held across differences in sex, ethnicity, and socioeconomic status. Failure to wear seat belts was associated with a higher use of alcohol, cigarettes, marijuana, and cocaine; more tolerance toward speeding and drinking while driving; less exercise; and more preference for fat in the diet. Our findings attest to the power of parent and peer influences in shaping seat-belt use by adolescents and suggest that not wearing seat belts can be conceptualized as one facet of a pattern of general risk-taking behavior. These findings suggest several possible educational interventions to increase seat-belt use by adolescents.