Both groups improved after treatment as measured by the Addiction Severity Index and treatment records, but American Indians showed greater reductions in arrests than non-American Indians. In the year before treatment admission, 36.9 percent of American Indians and 42.1 percent of non-American Indians had been arrested. The percentage of American Indians arrested after treatment admission showed a reduction rate of 14.7 percent; whereas, the reduction rate among non-American Indians was 8.7 percent. Pretreatment problems related to substance abuse were similarly severe for the two groups. Approximately half in both groups either completed treatment or stayed in treatment more than 90 days. American Indians in residential care had significantly shorter treatment retention. American Indians received fewer individual sessions and out-of-program services, particularly for alcohol abuse, but they were still generally satisfied with their treatment. The study demonstrated that greater service intensity for both individual and group services was critical for increasing treatment retention among American Indians in residential care. A sample of 368 American Indians and 368 non-American Indians were included in the current study. All were involved in the California Treatment Outcome Project, a multisite prospective substance abuse treatment outcome student that was part of the national Treatment Outcomes and Performance Pilot Studies enhancement. Most programs offered admission assessment and both individual and group alcohol and drug counseling. Thirty-nine programs were included in this analysis. Information was not available on whether they offered special services for American Indians. Study instruments and data measured treatment outcomes, treatment retention, treatment satisfaction, and services received. 4 tables and 35 references