OBJECTIVE: To assess the effectiveness of brief interventions in heavy drinkers by analyzing the outcome data and methodologic quality. DESIGN: (1) Qualitative analysis of randomized control trials (RCTs) using criteria from Chalmers' scoring system; (2) calculating and combining odds ratios (ORs) of RCTs using the One-Step (Peto) and the Mantel-Haenszel methods. STUDY SELECTION AND ANALYSIS: A MEDLINE and PsycLIT search identified RCTs testing brief interventions in heavy alcohol drinkers. Brief interventions were less than 1 hour and incorporated simple motivational counseling techniques much like outpatient smoking cessation programs. By a single-reviewer, nonblinded format, eligible studies were selected for adult subjects, sample sizes greater than 30, a randomized control design, and incorporation of brief alcohol interventions. Methodologic quality was assessed using an established scoring system developed by Chalmers and colleagues. Outcome data were combined by the One-Step (Peto) method; confidence limits and chi 2 test for heterogeneity were calculated. RESULTS: Twelve RCTs met all inclusion criteria, with an average quality score of 0.49 + or - 0.17. This was comparable to published average scores in other areas of research (0.42 + or - 0.16). Outcome data from RCTs were pooled, and a combined OR was close to 2 (1.91; 95% confidence interval 1.61-2.27) in favor of brief alcohol interventions over no intervention. This was consistent across gender, intensity of intervention, type of clinical setting, and higher-quality clinical trials. CONCLUSIONS: Heavy drinkers who received a brief intervention were twice as likely to moderate their drinking 6 to 12 months after an intervention when compared with heavy drinkers who received no intervention. Brief intervention is a low-cost, effective preventive measure for heavy drinkers in outpatient settings.