Background-Although research using clinical and convenience samples has shown alcohol use disorders (AUD) to be highly comorbid with tobacco dependence (TD), little work has examined this association prospectively using population-based data. The AUD-TD association was prospectively examined using data from the St. Louis Epidemiological Catchment Area (ECA) Study and its 1-year follow-up as well as from a 16-year follow-up on a subsample of ECA data.Method-Respondents were 3004 (2564, 85%, at Wave 2) participants in the St. Louis household ECA sample, including 444 participants at Year 16 follow-up. At baseline, the sample was predominately White (58%; 38% Black), female (60%), and 44.3 years. Past-year AUD and TD were diagnosed at all waves according to DSM-III criteria.Results-AUDs and TDs were cross-sectionally associated at Years 1, 2, and 16. Controlling for demographics, Year 1 TD prospectively predicted Year 2 AUD, and Year 1 AUD prospectively predicted Year 16 TD. We found evidence for prediction of onset and persistence of both AUD and TD at short-term but not long-term follow-up. Prospective findings were reduced and no longer reached significance when concurrent diagnoses at follow-up were included in the regression models.Conclusions-We observed short-term and long-term associations between AUD and TD. These associations were mediated through concurrent diagnoses with the other substance use disorder.