Context: The relative efficacy of antiandrogens for the treatment of hirsutism remains unclear. Objective: We performed a systematic review and metaanalyses of randomized controlled trials (RCTs) evaluating the effect of antiandrogens on hirsutism. Data Sources: We used librarian-designed search strategies for MEDLINE, EMBASE, and Cochrane CENTRAL (up to May 2006), review of reference lists, and contact with hirsutism experts to identify eligible RCTs. Study Selection: Eligible studies were RCTs of at least 6 months of antiandrogen use in women with hirsutism. Reviewers, with acceptable chance-adjusted agreement (κ = 0.72), independently assessed eligibility. Data Extraction: Reviewers used structured forms to assess and collect methodological quality (allocation concealment, blinding, and loss to follow-up) and study data. Data Synthesis: Of 348 candidate studies, 12 were eligible (18 comparisons). Their methodological quality was low. Random-effects metaanalyses showed that compared with placebo, antiandrogens reduce Ferriman-Gallwey scores by 3.9 [95% confidence interval (CI), 2.3-5.4; inconsistency (I2) = 0%]. When compared with metformin, spironolactone reduced hirsutism scores by 1.3 (CI, 0.03-2.6) and flutamide by 5.0 (CI, 3.0 -7.0; I2 = 0%). For these interventions, two to five women need to receive treatment for one to notice improvement. Spironolactone or finasteride in combination with contraceptives (1.7; CI, 0.1-3.3; I2 = 0%)or flutamide with metformin (4.6; CI, 1.3-7.9; I2 = 40%) appear superior to monotherapy with contraceptives and metformin, respectively. Only three RCTs reported patient self-assessments of hirsutism. Conclusions: Weak evidence suggests antiandrogens are mildly effective agents for the treatment of hirsutism. Copyright © 2008 by The Endocrine Society.