Objective: The American Indian Service Utilization, Psychiatric Epidemiology, Risk and Protective Factors Project (AI-SUPERPFP) provided estimates of the prevalence of DSM-III-R disorders and utilization of services for help with those disorders in American Indian populations. Completed between 1997 and 1999, the AI-SUPERPFP was designed to allow comparison of findings with the results of the baseline National Comorbidity Survey (NCS), conducted in 1990—1992, which reflected the general United States population. Method: A total of 3,084 tribal members (1,446 in a Southwest tribe and 1,638 in a Northern Plains tribe) age 15—54 years living on or near their home reservations were interviewed with an adaptation of the University of Michigan Composite International Diagnostic Interview. The lifetime and 12-month prevalences of nine DSM-III-R disorders were estimated, and patterns of help-seeking for symptoms of mental disorders were examined. Results: The most common lifetime diagnoses in the American Indian populations were alcohol dependence, posttraumatic stress disorder (PTSD), and major depressive episode. Compared with NCS results, lifetime PTSD rates were higher in all American Indian samples, lifetime alcohol dependence rates were higher for all but Southwest women, and lifetime major depressive episode rates were lower for Northern Plains men and women. Fewer disparities for 12-month rates emerged. After differences in demographic variables were accounted for, both American Indian samples were at heightened risk for PTSD and alcohol dependence but at lower risk for major depressive episode, compared with the NCS sample. American Indian men were more likely than those in NCS to seek help for substance use problems from specialty providers; American Indian women were less likely to talk to nonspecialty providers about emotional problems. Help-seeking from traditional healers was common in both American Indian populations and was especially common in the Southwest. Conclusions: The results suggest that these American Indian populations had comparable, and in some cases greater, mental health service needs, compared with the general population of the United States.