Background: This meta-analysis investigates the efficacy of pharmacological treatments for pathological gambling (PG). Methods: We searched for randomized, placebo-controlled trials examining pharmacotherapy of pathological gamblers. A fixed-effects model was used to calculate the standardized mean difference (SMD) of the benefit of medication (stratified by class) compared to placebo. Secondary analyses examined the effects of publication bias, year of publication and adherence to intention-to-treat (ITT) principles on reported efficacy of interventions. Results: Meta-analysis included 14 trials involving 1024 participants. Opiate antagonists demonstrated a small but significant benefit compared to placebo (SMD = 0.22 +/- 0.10 (95% CI: 0.03-0.41), z = 2.3, p = 0.02). The reported efficacy of opiate antagonists was significantly associated with non-adherence to ITT principles in trials and earlier year of publication. Other medications had non-significant effect sizes compared to placebo but similar in magnitude to opiate antagonists. Conclusions: Current trial data provides limited support for the use of any pharmacological agent in the treatment of pathological gambling.