Context: The effectiveness of personalized-feedback interventions to reduce problem drinking has been evaluated in several RCTs and systematic reviews. A meta-analysis was performed to examine the overall effectiveness of brief, single-session personalized-feedback interventions without therapeutic guidance. Evidence acquisition: The selection and analyses of studies were conducted in 2008. Fourteen RCTs of single-session personalized-feedback interventions without therapeutic guidance were identified, and their combined effectiveness on the reduction of problematic alcohol consumption was evaluated in a meta-analysis. Alcohol consumption was the primary outcome measure. Evidence synthesis: The pooled standardized-effect size (14 studies, 15 comparisons) for reduced alcohol consumption at post-intervention was d=0.22 (95% CI=0.16, 0.29; the number needed to treat=8.06; areas under the curve=0.562). No heterogeneity existed among the studies (Q=10.962; p=0.69; I2=0). Conclusions: The use of single-session personalized-feedback interventions without therapeutic guidance appears to be a viable and probably cost-effective option for reducing problem drinking in student and general populations. The Internet offers ample opportunities to deliver personalized-feedback interventions on a broad scale, and problem drinkers are known to be amenable to Internet-based interventions. More research is needed on the long-term effectiveness of personalized-feedback interventions for problem drinking, on its potential as a first step in a stepped-care approach, and on its effectiveness with other groups (such as youth obliged to use judicial service programs because of violations of minimum-age drinking laws) and in other settings (such as primary care).