Ninety-two intravenous drug users (IVDUs) were identified from a study of 1,640 relatives of treated alcoholics and felons. Nearly all of the IVDUs (90%) reported a lifetime history of some degree of physical, psychological, or social difficulty related to drug abuse, but only 35% had ever received treatment for drug abuse. Overall, compared to subjects with a history of substantial illicit drug use who had never injected, IVDUs were significantly more likely to report all drug-related problems assessed. Even in populations of drug users not selected through treatment, any history of intravenous (IV) drug use is strongly indicative of a lifetime occurrence of complications of drug use.