BACKGROUND Dutasteride is a dual inhibitor of type I and type II 5α-reductases and provides nearly complete suppression of dihydrotestosterone, which plays a key role in the aetiology and development of benign prostatic hyperplasia (BPH). Most knowledge about the efficacy and safety of dutasteride in BPH derives from three pivotal phase III studies conducted primarily in Caucasian populations. OBJECTIVE This study aimed to evaluate the efficacy and safety of dutasteride in Chinese adults with symptomatic BPH. METHODS This was a randomized, double-blind, parallel-group, placebo-controlled study conducted over 6 months, followed by an open-label extension of 12 months. A total of 253 BPH subjects with a total prostate volume (TPV) of ≥30 cm3, a maximal urinary flow rate (Q(max)) between 5 and 15 mL/s, and an American Urology Association Symptom Index (AUA-SI) score of ≥12 units were randomized to dutasteride 0.5 mg/day orally or matching placebo treatment in a 1:1 ratio. After 6 months, eligible subjects who volunteered to enter the open-label extension received dutasteride 0.5 mg/day orally. Changes in TPV, Q(max) and AUA-SI as well as drug safety were evaluated. RESULTS Dutasteride significantly reduced mean TPV compared with placebo at 3 and 6 months (both p < 0.05). At 6 months, mean TPV decreased by 17.14% versus 3.71% in the dutasteride and placebo groups, respectively. Numerically higher improvements in Q(max) and AUA-SI were observed in the dutasteride group at 3 and 6 months, but there was no statistically significant difference between treatment groups. However, ad hoc analysis indicated that, at 6 months, significantly higher proportions of subjects in the dutasteride group experienced a Q(max) improvement of ≥3 mL/s, or an AUA-SI improvement of ≥1 unit, compared with the placebo group (both p < 0.05). According to these criteria, the Q(max) responder rates were 33.63% and 19.83% in the dutasteride- and placebo-treated groups, respectively, and the AUA-SI responder rates were 87.61% and 76.92%, respectively. During the open-label extension, continuous improvements in TPV, Q(max) and AUA-SI were noted in both groups. Dutasteride was well tolerated with a low incidence of treatment-related adverse events over 18 months. CONCLUSIONS Dutasteride was effective compared with placebo in the treatment of symptomatic BPH among Chinese patients. The efficacy data from trials involving subjects of different ethnic origins showed some similarities. Dutasteride was generally well tolerated during the study period.