Questionnaire data from a sample of 3,023 adolescents indicated that over 60% of boys have tried smokeless tobacco, and 7% use it daily. Daily users reported an average of 5.3 uses per day. Among boys the prevalence of smokeless tobacco use in the past 6 months (18.8%) was higher than that for cigarette use (10.4%). For 86% of boys, the initial use of smokeless tobacco occurred in a social setting with other boys. Split-sample discriminant analyses identified peer use of smokeless tobacco as a discriminator between users and nonusers. Male triers of smokeless tobacco were discriminated from those who had never tried it by whether they had also tried smoking, intended to smoke, or had peers who used smokeless tobacco. Nine-month longitudinal data indicated that onset of smokeless tobacco use was not well predicted. Among daily users, the initial rate of use was the best prospective predictor of rate of use at follow-up (r = 0.576). Smokeless tobacco use was related to the use of other drugs, with 83% of male daily users indicating concurrent use of alcohol, marijuana, and/or cigarettes (tau = 0.354, 0.210, and 0.284, respectively). The use of smokeless tobacco was a prospective risk factor for the onset or increased use of cigarettes, alcohol, or marijuana.