Hirsutism is a common disorder with a major impact on quality of life. The most frequent cause is polycystic ovary syndrome. Effects of interventions (except laser and light-based therapies) were evaluated, including Grading of Recommendations Assessment, Development and Evaluation assessments. Searches included Cochrane Skin Group Specialised Register, CENTRAL in The Cochrane Library, Medline, Embase and five trials registers to June 2014. We included 157 randomized controlled trials (RCTs) with 10 550 participants. The majority were assessed as having a ‘high risk’ of bias (123 of 157). The quality of evidence was rated moderate to very low for most outcomes. Pooled data for an oral contraceptive (OCP) (ethinyl oestradiol and cyproterone acetate) compared with another OCP (ethinyl oestradiol and desogestrel) demonstrated that both treatments were effective in reducing Ferriman–Gallwey scores, but the mean difference (MD) was not statistically significant [−1·84, 95% confidence interval (CI): −3·86–0·18]. Flutamide was more effective than placebo in two studies (MD −7·60, 95% CI: −10·53 to −4·67 and MD −7·20, 95% CI: −10·15 to −4·25), as was spironolactone (MD −7·69, 95% CI: −10·12 to −5·26). Spironolactone appeared to be as effective as flutamide (two studies) and finasteride (two studies). However, finasteride and the gonadotropin-releasing analogues showed discrepant results in several RCTs. Metformin was ineffective. Cyproterone acetate combined with OCPs demonstrated greater reductions in Ferriman–Gallwey scores. Lifestyle interventions reduced body mass index but did not show improvement in hirsutism, and although cosmetic measures are frequently used, no RCTs investigating cosmetic treatments were identified. RCTs investigating OCPs in combination with antiandrogens or finasteride vs. OCP alone, or the different antiandrogens and 5α-reductase inhibitors are warranted.