Structured interviews were conducted with male drug addicts admitted to treatment programs in Baltimore and New York City. Subjects were asked to provide information on criminal activity and drug use for the 2-year period immediately preceding their first period of drug addiction, defined as the preaddiction period. Subjects were also asked to provide the same information for each period of addiction and nonaddiction. Criminal activity was measured using the concept of crime days per year at risk. In addition, subjects were asked about their use of various narcotic and nonnarcotic substances. Significant decreases over successive addiction periods were found for four of five crime categories: theft, violence, drug distribution, and other crime (primarily gambling). These results appeared to be accounted for by a disproportionately high level of crime during the first addiction period. Criminal activity, notably theft and violence, decreased over successive nonaddiction periods, although not significantly. A particularly large addiction versus nonaddiction disparity in crime rates was found for Hispanic addicts, revealing a low propensity for crime when not addicted. With regard to drug use over the addiction career, the most dramatic increases over time were found for illicit methadone and cocaine, while heroin and marijuana use rates declined. 32 references and 5 tables