The sample consisted of consecutive male admissions to a methadone maintenance treatment program in Pennsylvania. Each of the subjects was interviewed during a 9-month period by specially trained interviewers. The interview included detailed questions about the frequency of specific types of drug use during each subject's addiction career. An addiction period was defined as a time when a subject used opiates at least 16 days per month. Three patterns of polydrug abuse were found. During the first addiction period, 39 percent used opiates and were not regular users of nonopiate drugs (amphetamine, cocaine, valium, barbiturates, quaaludes, and Talwin-Pyribenzamine); 41 percent used one nonopiate regularly in addition to opiates; and 20 percent used two or more nonopiates in addition to opiates. During the first nonaddiction period, these figures dropped. Thirty-eight percent used no opiates or nonopiates, 26 percent used opiates plus one nonopiate, and 10 percent used opiates plus two or more nonopiates. These patterns of use were stable over time. As the subjects moved from addiction to nonaddiction, the largest number of addicts either remained in their addiction pattern of abuse or moved to a less abusive pattern of drug use. 5 data tables and 7 footnotes. (Author abstract modified)