OBJECTIVE Open prostatectomy (OP) is a valid option for the surgical treatment of large prostates in the absence of holmium laser enucleation. The most frequent complication of OP is intra- and perioperative bleeding. Preoperative use of dutasteride has been shown to reduce vascularity and perioperative bleeding in transurethral resection of the prostate (TUR-P). However, there has been no study addresing this effect in OP. The aim of this study was to evaluate whether pretreatment with dutasteride for 6 weeks before OP can reduce surgical blood loss. METHODS Data of 218 patients with benign prostatic hyperplasia (BPH) who underwent OP was investigated retrospectively. Of the 218 patients, 46 were treated with dutasteride for at least 6 weeks and the rest were dutasteride naïve. Age, prostate volume, prostate-specific antigen (PSA) levels, coagulation tests, platelet counts, pre- and postoperative hemoglobin (Hb) levels, and transfusion history were recorded. Blood loss was estimated as follows: preoperative Hb (-) postoperative Hb (+) amount of transfusion. The 2 groups were compared by independent samples t-test and a p value of 0.05 was considered significant. RESULTS The groups were similar in terms of age, prostate volume, platelet counts, coagulation tests, and postoperative Hb levels. Preoperative Hb levels were lower in the dutasteride group (13.4 vs. 14.3, p=0.002) and amount of bleeding (-2.72 g/dL vs. -1.93 g/dL, p= 0.01) was shown to be significantly lower in dutasteride group. CONCLUSIONS Our results showed that pretreatment with dutasteride for 6 weeks before OP considerably reduces perioperative surgical bleeding. Further prospective randomized trials should be conducted to confirm the effectiveness of such treatment.