Dutasterid is a novel effective inhibitor of 5-alpha reductase of both types which can be used in patients with large (more than 80 cm3) prostatic adenoma to prevent intra- and postoperative hemorrhagic complications before transurethral resection of the prostate (TUR). The trial included 70 males aged 67-82 years (mean age 74 years) with large size prostatic adenoma (more than 80 cm3) having indications for prostatic TUR. Patients with coagulopathy, suspected prostatic cancer, previous treatment with 5-alpha reductase inhibitors were not included. Group 1 (n=35) received dutasterid in a dose 0.5 mg/day for 38 days, on the average, before operation, and alpha-adrenoblocker tamsulosin in a dose 0.4 mg to prevent acute urine retention. Group 2 (n=35) received only alpha-adrenoblocker tamsulosin. Comparison of intraoperative indices showed that group 1 demonstrated shorter duration of the operation (62 vs. 79 min), more amount of the removed tissue (92 vs. 85 g), less volume of the irrigation liquid (16.7 vs. 19.3), shorter duration of urethral catheter tension (10.4 vs. 19.3), less volume of intraoperative blood loss (93.6 ml vs. 138.6 ml, p < 0.05). As a result, hospitalization time, time of urinary bladder drainage were also reduced in group 1. Postoperative hemorrhagic complications were not registered. We recommend to begin dutasterid administration in a dose 0.5 mg for 1 month before TUR not only for patients with larger prostate (greater than 80 cm3) but with smaller prostates (30-80 cm3) for prevention of hemorrhagic complications and better conditions for surgery.