Substance abuse treatment is defined as "formal organized services for individuals who have abused drugs, including alcohol." These services are designed to alter specific physical, mental, or social functions of those receiving treatment by reducing disability or discomfort, as well as to ameliorate the signs or symptoms caused by drug abuse. Intensive treatment services include treatment planning, individual and group counseling, habilitative and rehabilitative services, collateral services, advocacy and referral, social and recreational activities, and optional self-help group participation. The report includes background information on indicators of the substance abuse problem within the California Department of Corrections and responses to the problem, along with a general description of the current adult prison population and a brief historical review of in-prison substance abuse treatment program effectiveness. The report indicates that recent data for three California prison-based programs -- the Substance Abuse Program at R. J. Donovan Correctional Facility, the Forever Free Program at the California Institution for Women, and the female civil addict intensive treatment program at the California Rehabilitation Center -- all indicate that the return to State prison custody rates are substantially lower for treatment participants. If the in-prison treatment and recovery in community programs upon parole, the outcome is even more favorable. Further, treatment participants who are returned to custody generally remain on parole longer prior to a first return. 6 tables and 30 references