The interviews solicited information on the amounts and types of crimes that were committed during the addict's longest period of active addiction to opiates, their derivatives, and synthetics as well as the first period of nonaddiction. Crimes were classified as theft, violence, drug sales, deception/forgery, and "other." Several measures of criminal activity were used; all embodied the concept of crime days per year at risk. Addicts were compared by race/ethnicity (black, white, and Hispanic) within cities as well as across cities through the use of one-way analysis-of-variance procedures. Addict crime rates were also compared for the period of active addiction and nonaddiction. The amounts and types of crime committed were to some extent dependent on race/ethnic group and geographic location, but to a greater extent on whether the individual was actively addicted to narcotics. During periods of active addiction, crime rates were substantially higher in a number of areas. 2 tables and 16 references