Objective: This study examines the relation between cognitive-motivational variables and self-reported health behaviours among adolescents. Design: Cross-sectional survey of adolescents via questionnaires delivered in classrooms. Setting: One large junior high school and two senior high schools located in the Memphis area. Method: Data from 257 7th to 12th graders were used to determine their practice of health behaviours as well as their perceptions of health status and vulnerability, optimism and rebelliousness/risk taking. Results: Adolescent males and females who were less rebellious and had better health perceptions reported healthier behavioural practices. A stronger significant inverse relationship between perceived vulnerability and health behaviour scores was found for females. Optimism was significantly and positively correlated with health behaviour scores only among females. Adolescents in lower grades obtained higher health behaviour scores than adolescents in higher grades. Males had higher rebelliousness scores than females. Demographic and cognitive-motivational variables accounted for 26 per cent of the variance in health behaviour scores. Conclusion: Cognitive-motivational factors should be considered when designing health promotion programmes for adolescents. (Contains 4 tables.)