Consistent with the overall evaluation plan, this study introduces a new comparison group to the series, namely inmates who volunteered for the program, but who failed to complete it for a variety of reasons ranging from volunteering out to being removed for disciplinary reasons. The other comparison groups include pre-shock inmates and inmates who were legally eligible for shock incarceration, but who did not enter the program. Using a 24-month period of exposure in the community criteria, the shock incarceration graduates were returned to custody in 44.1 percent of cases, pre-shock inmates were returned 44.8 percent of the time, the control group considered for shock treatment returned in 47.5 percent of the cases, and the group removed from shock before completion returned to custody 58.8 percent of the time. The findings indicate that, despite a shorter incarceration period, inmates who participate in the shock incarceration program are returned to custody at lower or similar rates to comparable groups. The shorter incarceration period has saved the Department approximately $150 million as of January 31, 1991. 2 tables