Results indicate that higher levels of self-efficacy at intake were related to increased odds of reported heroin abstinence and a lower number of drugs used at 1-year followup. Greater levels of ethnic identity were related to a greater number of drugs used at followup. No significant effects were found for spirituality. Ethnic minority populations are rapidly expanding in the United States. There is increasing concern over whether standard health care services, including substance abuse treatment, account for important cultural influences. Few studies have focused on the impact of cultural factors on substance abuse treatment with little known about the generalizability of existing findings to ethnic minority populations. By examining the effects of ethnic identity, spirituality and self-efficacy on substance abuse treatment outcomes among Hispanic American methadone maintenance clients, the importance of cultural influences and the generalizability of a more commonly studied treatment factor could be assessed. This study prospectively examined the effects of 2 cultural factors, ethnic identity and spirituality on substance abuse treatment outcomes among 114 Hispanic American clients enrolled in methadone maintenance treatment. In addition, the study examined whether a commonly studied treatment factor, self-efficacy significantly influenced treatment outcomes. Tables and references