Palmer (1983) identifies two general positions on treatment modalities in prison: the "skeptical" and "sanguine" camps. The "skeptical" perspective holds that relatively few treatment programs work, and those that do account for negligible reductions in recidivism. The "sanguine" perspective acknowledges that although rehabilitation programs have not been very effective to date, there is evidence that many programs provide positive effects for selected portions of the offender population. Current assessments of treatment modalities note variations in the success of various modalities with differing offender types. Group therapies are particularly popular in prison settings because they are cheaper than individual therapies. This paper describes five types of therapeutic groups and assesses treatment modalities for drug addiction, sex offenders, violent offenders, and alcoholism. 40 references.