BACKGROUND Non-steroidal antiandrogens and castration are the main therapy options for advanced stages of prostate cancer. However, debate regarding the value of these treatment options continues. OBJECTIVE To assess the effects of non-steroidal antiandrogen monotherapy compared with luteinising hormone-releasing hormone agonists or surgical castration monotherapy for treating advanced stages of prostate cancer. METHODS We searched the Cochrane Prostatic Diseases and Urologic Cancers Group Specialized Register (PROSTATE), the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, Web of Science with Conference Proceedings, three trial registries and abstracts from three major conferences to 23 December 2013, together with reference lists, and contacted selected experts in the field and manufacturers. METHODS We included randomised controlled trials comparing non-steroidal antiandrogen monotherapy with medical or surgical castration monotherapy for men in advanced stages of prostate cancer. METHODS One review author screened all titles and abstracts; only citations that were clearly irrelevant were excluded at this stage. Then, two review authors independently examined full-text reports, identified relevant studies, assessed the eligibility of studies for inclusion, assessed trial quality and extracted data. We contacted the study authors to request additional information. We used Review Manager 5 for data synthesis and used the fixed-effect model for heterogeneity less than 50%; we used the random-effects model for substantial or considerable heterogeneity. RESULTS Eleven studies involving 3060 randomly assigned participants were included in this review. The quality of evidence is hampered by risk of bias. Use of non-steroidal antiandrogens decreased overall survival (hazard ratio (HR) 1.24, 95% confidence interval (CI) 1.05 to 1.48, six studies, 2712 participants) and increased clinical progression (one year: risk ratio (RR) 1.25, 95% CI 1.08 to 1.45, five studies, 2067 participants; 70 weeks: RR 1.26, 95% CI 1.08 to 1.45, six studies, 2373 participants; two years: RR 1.14, 95% CI 1.04 to 1.25, three studies, 1336 participants), as well as treatment failure (one year: RR 1.19, 95% CI 1.02 to 1.38, four studies, 1539 participants; 70 weeks: RR 1.27, 95% CI 1.05 to 1.52, five studies, 1845 participants; two years: RR 1.14, 95% CI 1.05 to 1.24, two studies, 808 participants), compared with medical or surgical castration. The quality of evidence for overall survival, clinical progression and treatment failure was rated as moderate according to GRADE. Predefined subgroup analyses showed that use of non-steroidal antiandrogens, compared with castration, was less favourable for overall survival, clinical progression (at one year, 70 weeks, two years) and treatment failure (at one year, 70 weeks, two years) in men with metastatic disease. Use of non-steroidal antiandrogens also increased the risk for treatment discontinuation due to adverse events (RR 1.82, 95% CI 1.13 to 2.94, eight studies, 1559 participants), including events such as breast pain (RR 22.97, 95% CI 14.79 to 35.67, eight studies, 2670 participants), gynaecomastia (RR 8.43, 95% CI 3.19 to 22.28, nine studies, 2774 participants) and asthenia (RR 1.77, 95% CI 1.36 to 2.31, five studies, 2073 participants). The risk of other adverse events, such as hot flashes (RR 0.23, 95% CI 0.19 to 0.27, nine studies, 2774 participants), haemorrhage (RR 0.07, 95% CI 0.01 to 0.54, two studies, 546 participants), nocturia (RR 0.38, 95% CI 0.20 to 0.69, one study, 480 participants), fatigue (RR 0.52, 95% CI 0.31 to 0.88, one study, 51 participants), loss of sexual interest (RR 0.50, 95% CI 0.30 to 0.83, one study, 51 participants) and urinary frequency (RR 0.22, 95% CI 0.11 to 0.47, one study, 480 participants) was decreased when non-steroidal antiandrogens were used. The quality of evidence for breast pain, gynaecomastia and hot flashes was rated as moderate according to GRADE. The effects of non-steroidal antiandrogens on cancer-specific survival and biochemical progression remained unclear. CONCLUSIONS Currently available evidence suggests that use of non-steroidal antiandrogen monotherapy compared with medical or surgical castration monotherapy for advanced prostate cancer is less effective in terms of overall survival, clinical progression, treatment failure and treatment discontinuation due to adverse events. Evidence quality was rated as moderate according to GRADE. Further research is likely to have an important impact on results for patients with advanced but non-metastatic prostate cancer treated with non-steroidal antiandrogen monotherapy. However, we believe that research is likely not necessary on non-steroidal antiandrogen monotherapy for men with metastatic prostate cancer. Only high-quality, randomised controlled trials with long-term follow-up should be conducted. If further research is planned to investigate biochemical progression, studies with standardised follow-up schedules using measurements of prostate-specific antigen based on current guidelines should be conducted.