In recent years, peer recovery support services have become an accepted part of the treatment of substance use disorders, providing a more extensive array of services than typically associated with mutual support groups. Peer providers may help consumers set recovery goals, develop a plan, and work toward and maintain recovery. In this literature review, the last in the Assessing the Evidence Base (AEB) Series, the authors review the evidence supporting peer recovery support services, noting that more research is needed to distinguish the effects of peer recovery support from other recovery support activities.