Participants in a work release TC treatment program during the transitional period between prison and the community were significantly less likely to have had a new arrest or to have returned to incarceration; and they had significantly longer times before arrest or returning to custody, even when controlling for demographic differences and differences in drug-use, employment, and criminal histories. The time before arrest was more than 50 percent longer than for those without treatment. Those with a more extensive criminal history showed particular benefits from the treatment program. Older offenders showed the most benefit from an aftercare component of work-release treatment. Both the regular work release and the work release TC were 6-month programs that included both men and women with separate secured evening quarters. In regular work release, inmates were released during the day and required to return to the dormitories each evening. The TC consisted of a "family setting" of individual chores, group responsibilities, and discipline. In addition to intensive therapeutic community treatment, clients prepared for and obtained employment in the community. The study sample was drawn from inmates classified in the Delaware correctional system as approved for work release with a recommendation for drug treatment between 1991 and 1998. The research protocol included baseline and multiple follow-up interviews, with urine testing at each interview. The most relevant items in the interviews pertained to the time to new arrest and the time to any return to custody. 3 tables and 35 references