A primary goal of case management is to coordinate services across treatment settings and to integrate substance abuse services with other types of services offered in the community, including housing, mental health, medical, and social services. However, case management is a global construct that consists of several key dimensions, which include extent of case management coverage, the degree of management of the referral process, and the location of case management activity (on-site, off-site, or both). This study examines the relationship between specific dimensions of case management and the utilization of health and ancillary social services in outpatient substance abuse treatment. In general, results suggest that more active case management during the referral process and providing case management both on-site and off-site are most consistent with our predictions of greater use of health and ancillary social services by substance abuse clients. However, these effects are specific to general health care and mental health services. Case management appears to have little effect on use of social services or aftercare plans. © 2007 National Council for Community Behavioral Healthcare.