Participants were interviewed in 1973 and 1974 to gather information about their demographic characteristics, drug use, and self-reported criminal histories. Their arrest data were collected from official records. The analysis focused on the general effect of addiction on criminal activity; the effect of addiction on specific offense categories; and the variations of the effects of addiction on criminal activity relative to the age of onset of addiction, race, and gender. Results revealed that the sample was primarily male (83.5 percent) and Hispanic (40 percent). Almost one-fourth of the participants were 22-24 years old; three-fourths were age 30 or younger. significant increases in criminal activity associated with the onset of addiction. The increases occurred in violent crimes as well as property crimes and drug law offenses. Some differences were apparent according to the age of onset of addiction, race, and gender, but the research design did not permit definitive conclusions regarding these differences. Tables, notes, and 14 references (Author abstract modified)