This article discusses the effectiveness of alcohol and other drug abuse treatment management by health care maintenance organizations (HMOs) and other primary care managers. After discussing that many United States Medicaid programs are dealing with issues of how to introduce managed care approaches to alcohol, drug abuse, and mental health treatment systems, the authors present a brief literature review of studies focusing on HMOs and Primary Care Case Management (PCCM) models. This research examined the role of medical plans in managing alcohol/other drug abuse (AOD) treatment in Michigan’s Medicaid program. Surveying a random sample of outpatient AODs that treated Michigan’s Medicaid clients in 1997, the authors found that clients enrolled with HMOs or other primary care “gatekeepers” were seen as receiving somewhat worse or much worse care than did clients with Physical Sponsored Plans. Treatment providers further indicated that medical “gatekeeper” programs provided only fair to average services in terms of coordinating alcohol and other drug abuse treatment with primary patient care and with mental health services. The authors indicate that these findings suggest that further work must be done in order to take the issue of continuity and coordination of patient care into consideration with dealing with AOD clients using HMOs and PCCMs. Figures, tables, references