This prospective study (n=190) examined correlates of alcohol use from baseline data of a longitudinal trial conducted among moderate and heavy alcohol users receiving methadone maintenance therapy (MMT). The sample included MMT clients who were 18-55 years of age, and were receiving MMT from five large methadone maintenance clinics in the Los Angeles area. Half of the sample was heavy drinkers and nearly half (46%) reported heroin use. Using a structured questionnaire, correlates of heavy alcohol use included White and Hispanic ethnicity, and fair or poor physical health combined with older age (> or =50 years). We also found that MMT clients who were younger than 50 years, regardless of health status, were more likely to be heavy drinkers. Compared with moderate alcohol consumers, a greater number of heavy alcohol users also experienced recent victimization. To optimize MMT, alcohol screening should be part of routine assessment and alcohol treatment should be made available within MMT programs. Moreover, special consideration should be provided to the most vulnerable clients, such as the younger user, those with a long-term and current history of heavy drug use, and those victimized and reporting fair or poor health. In addition, promoting attention to general physical and mental health problems within MMT programs may be beneficial in enhancing health outcomes of this population.