Subjects were 1,068 adolescents in grades 10, 11, and 12 at testing during the fourth year of a longitudinal study. The present sample included 847 of these subjects tested during the fifth year. Results indicate a nonstepwise progression in the lifetime experiences of negative drug reactions to four classes of drugs (alcohol, marijuana, hallucinogens, and phencyclidine), suggesting that acute adverse reactions to marijuana are not a necessary precondition to having such experiences with hard drugs. Causal effects did not appear to exist between drug use and acute adverse reactions over time. The experience of adverse effects did not predispose an individual to stop using drugs of various types. While adverse reactions were not linked to psychological distress, distress was a precursor to increased drug use over time. Results suggest that bad drug experiences of all types are positively correlated to one another to a higher degree and support the interpretation that adverse drug reactions are caused by a general factor or predisposition to such reactions. Implications for drug abuse prevention programs are discussed. 3 tables, 1 figure, and 30 references. (Author abstract modified)