The research analyzed the influence of protective and risk factors on five measures of drug use: overall involvement in drugs, frequent alcohol use, frequent use of illegal drugs, frequent drug abuse, and the quantity of daily cigarette consumption. For each measure, the research hypothesized that an index of risk factors would increase the likelihood of the occurrence of problem behavior and that an index of protection would result in a reduction. It was also hypothesized that under conditions of high risk the effect of protection would moderate the influence of risk factors more strongly than under conditions of low risk. The participants completed self-report questionnaires containing more than 60 risk and protective measures. Regression analyses revealed support for the hypothesis of separate risk and protective factor main effects for all categories of drugs. Findings also indicated moderate to strong interaction effects in the sense of a moderating influence of protection. Findings indicate the need for comprehensive programs that try to change the possible harmful effects of many interrelated problem behaviors and the underlying risk and protective factors that these behaviors have in common. Tables, appended tables, and 45 references (Author abstract modified)