Subjects were 994 adolescents in grades 10, 11, and 12 during the fourth year of a longitudinal study. Risk factors examined included low grade point average, lack of religiosity, early alcohol use, low self-esteem, psychopathology, poor relationships with parents, lack of social conformity, sensation-seeking, perceived peer drug use, and perceived adult drug use. Results indicate that those with three or fewer risk factors were less likely than the total sample to be heavy users of hard drugs, whereas those with five or more were more likely to be at least weekly users of hard drugs. Those with seven or more risk factors were over nine times as likely to be heavy users of hard drugs compared to the general sample. Partial correlations between fourth year risk factors and drug use in the fifth year indicate that year-4 risk factors were clearly related to increased use of all substances over time. The strongest effects were for alcohol and hard drugs, the weakest effect was for cigarettes. 3 figures, 5 tables, and 53 references.