AbstractAs many as one-half to three-fourths of homeless persons have diagnoses of alcohol or other drug dependence. Rates of alcohol and other drug use disorders, and the social costs associated with untreated substance disorder, are higher among homeless than nonhomeless persons. Despite the high level of need for treatment, relatively few substance-abusing homeless individuals receive treatment for their drug problems, suggesting difficulties in accessing treatment. This study addresses access by focusing on the select group of homeless drug users who have overcome barriers to enter the substance abuse treatment system in California and by examining differences between these homeless treatment clients and nonhomeless drug-using clients. Major findings from bivariate and logistic regression analyses performed on 187 homeless and 1,820 nonhomeless treatment clients are that homeless clients were more likely than nonhomeless clients to have a primary drug problem of cocaine/crack and to be injecting methamphetamine and other amphetamines, and that they were no less likely to complete their treatment program. An implication of this study is that homeless persons with primary drug problems appear to have no less commitment to achieving treatment goals than their nonhomeless counterparts.†This study was facilitated by a RAND Drug Policy Research Center postdoctoral fellowship to the first author funded by the General Mills Foundation and the Ford Foundation. The authors would like to thank the California Department of Alcohol and Drug Programs, the UCLA Drug Abuse Research Center, and Carol Edwards and C. Peter Rydell of RAND Corporation.