The subjects were a stratified random sample from 6,149 known narcotic users arrested or identified by police between 1952 and 1976. The sample was unselected for criminality but stratified by race and year of police contact. To be included in the study, subjects must have used narcotics on at least 4 days a week for at least 1 month while in the community. Subjects described their narcotic addiction, abstinence, and incarceration periods, with criteria for successive addiction periods being the same as that for inclusion in the study. All crimes reported by the subjects were placed in one of the following categories: theft, violence, drug dealing, confidence games, and other. The application of numerical taxonomic methods yielded eight addict types for addiction periods: marginal criminals, drug dealers, thieves, illegal gamblers, con men, violent, super con men, and super violent. Six types were identified for nonaddiction periods: marginal criminals, drug dealers, thieves, illegal gamblers, con men, and violent. The subjects committed a great deal of crime by any absolute standard. Fewer crimes were committed during nonaddiction periods, but individual crime patterns tended to remain constant. 3 tables and 48 references.