The P3 features case management and substance abuse treatment provided by local vendors to California parolees who are living in San Diego County. P3 established a contract between the County of San Diego Alcohol and Drug Services and a private vendor, Mental Health Systems, Inc., to provide outreach and case management services to parolees. This recidivism evaluation compared P3 participants to a corresponding nonparticipant group on return-to-prison rates. The P3 treatment group consisted of all parolees who entered P3 and stayed in P3 at least 7 days or longer from April 1994 through August 1995. Parolees from the comparison group were matched on type of parole and date released from prison. There were 357 matched parolees in both the P3 and comparison groups. A 1-year follow-up period was used to calculate recidivism rates of both the P3 and comparison groups. The evaluation found that parolees with substance abuse problems who participated in P3 were less likely to be returned to prison within 1 year following admission to treatment. There was a 28-percent reduction in the odds of P3 participants being returned to prison. Also, P3 participants who were returned to prison remained on parole for a longer period of time before returning to prison. The difference of nearly 3 months is statistically significant. Data also show that participants who completed P3 and those who had stable living or employment situations when they left P3 had statistically lower recidivism rates. Comments are offered on the evaluation methodology, and suggestions are made for improving it. 5 tables