Data were collected on the last personal overdose (117 cases), the last witnessed overdose (167 cases), and the last witnessed fatal overdose (55 cases) and on the different drugs that had been involved with these overdoses. The participants were 196 men and 116 women; 290 had been involved in heroin use in the year prior to interview. Seventy-six percent had used methadone, 60 percent had used cocaine, and 38 participants drank alcohol heavily. Most participants had extensive histories of intravenous drug use. Heroin was involved in 83 percent of the last personal overdoses, 90 percent of the last witnessed overdoses, and 80 percent of the last witnessed fatal overdoses. In contrast, other opiates were involved in only 18 percent of the last personal overdoses, 8 percent of the last witnessed overdoses, and 26 percent of the last witnessed fatal overdoses. Methadone accounted for about half of the overdoses involving other opiates. Overdoses involving a combination of heroin and a non-opiate were common. Findings indicated that methadone was remarkably infrequently reported as solely or partly responsible for either personal overdoses, witnessed overdoses, or witnessed fatal overdoses, considering the wide extent of methadone prescribing to this group. Figures, tables, and 35 references (Author abstract modified)