The objective of this study was to review the evidence for the efficacy and toxicity of naltrexone, a treatment of alcohol dependence. A systematic review and meta-analysis of randomized controlled trials of naltrexone used in the treatment of alcohol dependence was conducted. We searched MEDLINE, EMBASE, PsychLIT and the Cochrane Controlled Trials Registry for articles published between 1976 to January 2001. The manufacturer of naltrexone was asked to submit additional complete trial reports not in the literature. We analysed data from seven studies that compared naltrexone to placebo. The meta-analysis of benefit indicates that naltrexone is superior to placebo. Subjects treated with naltrexone experience significantly fewer episodes of relapse, and significantly more remain abstinent when compared to placebo-treated subjects [risk difference of relapse rates = -14% [95% confidence interval (CI): -23%, -5%]; and risk difference of abstinence rates = 10% (95% CI: 4%, 16%)] after 12 weeks of treatment. The naltrexone-treated subjects also consume significantly less alcohol over the study period than do placebo-treated subjects. There is no significant difference between naltrexone and placebo in terms of the number of subjects with at least one adverse event or the number of subjects who discontinued the trial due to an adverse event.