On a typical day in 2008, 776,573 individuals were behind bars in nearly 3,500 U.S. jails. Yet the potential benefits of social services in achieving lower recidivism rates and successful reintegration are understudied in jail populations. This three-year study investigated the effects of collaboration-based in-jail services and postrelease transitional services provided by the Allegheny County Jail Collaborative (ACJC). The results included a significantly lower recidivism rate among inmate participants, similar service benefits across racial groups, and successful reintegration into community life among a large majority of participants. At 12 months postrelease, participants had a 50 percent lower recidivism rate than members of the matched comparison group, who were unexposed to the intervention, and multiple indicators showed successful reintegration. This reduced rate would save the county an estimated $5.3 million annually, largely due to increased public safety and lower victimization costs. Data sources included the ACJ's historical inmate data sets from the pre-ACJC and post-ACJC intervention periods, three postrelease face-to-face survey interviews, and focus group sessions with former inmate participants and the study interviewers.The critical importance of social workers in rehabilitative efforts with jail inmates is discussed along with recommendations and implications for policy, practice, and research.