The study sample consisted of all 277 patients who had been admitted to New York City's St. Luke's Hospital methadone clinic from its inception in March 1966 to January 1, 1972. Information on 269 patients was submitted to the New York City Police Department for arrest record research. Arrest records were obtained for 210 patients or 78 percent of all the names submitted. The records were studied longitudinally in relation to various stages of narcotic use. Predominantly noncriminal before addiction, the patients had progressively increased rates of annual arrests after addiction started. Increased arrests were primarily for violations of the dangerous drug laws, prostitution, violence, property crime, and misbehavior. During methadone maintenance treatment, the frequencies of dangerous drug use, prostitution, and property crimes decreased sharply, approaching their incidence in the control population, while misbehavior and violence remained somewhat higher than controls. The study documents a complex interrelationship between addiction and crime in a lower class, predominantly minority group of urban addicts. 5 figures, 3 tables, and 11 references