Substance abuse prevalence rates for Latinos/as generally mirror those of the general U.S. population; however, a number of indicators of assimilation to U.S. culture as well as sociodemographic variables predict substance use and abuse among this group. Latinos/as have poorer outcomes in substance abuse treatment programs. Yet there is little empirical evidence that explains the problems these individuals experience in treatment, and there are few studies on the use and effectiveness of mutual help groups among this population. New developments in the conceptualization and measurement of acculturation will lead to a greater understanding of the role of culture in the prevalence and treatment of substance-related problems.