While data on the onset of cigarette smoking among younger adolescents has been investigated extensively, it is less clear whether the same social factors influence older adolescents. To examine these social factors, as well as the influence of personality and beliefs, 1,977 high school participants in an anti-smoking study completed a questionnaire relating to smoking behavior, family and peer smoking behavior, and attitudes and beliefs. Saliva specimens were also examined. Of these subjects, 1,705 remained non-smokers at the 4 month posttest, while 277 (14 percent) began smoking. Results suggested that even during late adolescence, peer influence remains the predominant predictor of smoking. As with younger children, rebelliousness and family smoking also figured predominantly in smoking onset. Perceptions of social morality significantly distinguished smokers from non-smokers. While the findings were significant, it appeared easier to predict who would not become a smoker than who would become one, in part due to the transitory nature of experimental smoking. (JAC)