Aim of the study: To assess the effects of 5-α-reductase inhibitor (finasteride) on per operative blood loss in patients with BPH undergoing TURP by measuring preoperative and postoperative Hb by comparison with control cases. Methodology: A total of 50 patients of Benign Prostatic Hyperplasia (BPH) planned for Trans-Urethral Resection of Prostate (TURP) having a prostate size of more than 40 grams on trans-abdominal ultrasonography an\or transrectal ultrasonography with PSA of less than 0.4 ng\dl was randomized into 2 groups, each group having 25 patients. The finasteride group (Group A) was prescribed oral 5 mg of finasteride daily for 2 weeks before surgery. The control group (Group B) did not receive any agent. After 2 weeks, TURP was performed and variables were recorded. Results: There was no significant difference in the mean age of patients, prostate volume, PSA and preoperative hemoglobin level in both groups, however, significant difference was found for postoperative hemoglobin level with highly significant p-value=0.001 in that postoperative hemoglobin was dropped more in control group, and the rate of blood transfusion was more in the control group (7% for the control group while 1% for study group) besides these, amount of irrigation fluid used and duration of irrigation was more in the control group. Conclusion: The 5-α-reductase inhibitors (finasteride) reduces intraoperative and postoperative blood loss in patients with BPH undergoing TURP if given two weeks before surgery as well as decrease rate of blood transfusion, amount of irrigation fluid used and duration of irrigation needed to clear hematuria postoperatively.