An assessment of 15 community-based outpatient treatment programs for chemically dependent adult offenders was undertaken using the format of the University of Maryland's 1997 report to the US Congress. The review finds less optimism about the effectiveness of this type of drug treatment than previous reviews. The assessment of these studies indicated that programs that increase the supervision, monitoring, or control over offenders in the community are not effective in reducing recidivism. There is insufficient evidence to determine whether outpatient treatment alone, specific components of the treatment (such as acupuncture), or aspects of the treatment (intensity) are effective in reducing criminal activity. Outpatient treatment designed as aftercare to prison-based therapeutic communities (TCs) is shown to be effective. However, it is unclear whether this is the effect of the TC, the length of treatment, or the combination of the TC and the aftercare. (C) 2001 Elsevier Science Inc. All rights reserved.