Two-hundred and sixty eight opioid addicts completed a 2.5 year follow-up during which we examined the psychosocial antecedents and consequences of leaving, reentering and remaining in treatment. Compared to those addicts who obtained more sustained treatment, the addicts who were only detoxified had fewer psychological problems and were more often male, black and younger. These baseline differences complicated comparisons between these minimally treated addicts and the rest, but among those who had more than minimal treatment, continuous treatment was better than intermittent treatment in controlling substance abuse and legal problems. Further analyses involved dividing the 30 months of follow-up into 6 month blocks and comparing the 6 months before, during and after leaving or reentering treatment. We found that addicts left treatment at periods of relative abstinence and good psychosocial adjustment, although they increased their alcohol abuse during the period of leaving treatment. During the 6 months after leaving, patients often returned to drug abuse and then rapidly deteriorated in social adjustment. When reentering treatment, the majority (75%) stayed for over 6 months and improved steadily in most areas. At reentry patients also had less criminal activity, less physical disability, and less opiate use suggesting a carry-over of treatment benefits, but they had more problems with their spouse and more alcohol and cocaine use than they had when first entering treatment suggesting new precipitants for reentry into treatment.