Better understanding of the diverse factors that predict alcoholism treatment outcomes is essential to improving treatment strategies. Patients accepted for treatment at a multimodality program were interviewed and followed-up at three months and one year after admission. The study tested a set of hypotheses relating to the effects on drinking outcomes of treatment modality, modality matching, treatment retention, aftercare, self-help group participation and patient attributes at admission. Drinking frequency diminished substantially between baseline and the two follow-ups. Outcomes for inpatient were better than for outpatient treatment in bivariate analysis, but outcomes for these modalities were equal after adjusting for the effect of patient-treatment mismatching. Aftercare treatment, time in treatment for outpatients, community 12-Step group participation, and several patient attributes such as motivation for change and psychiatric severity significantly predicted drinking outcomes at one or both follow-ups. Clinical implications of the results are discussed.