OBJECTIVE: To evaluate the clinical effectiveness of dutasteride in the treatment of gross haematuria due to benign prostatic hyperplasia and adenocarcinoma of the prostate by determining the time it took haematuria to stop and the amount of irrigation fluid used while using dutasteride as the primary mode of treatment. BACKGROUND: Dutasteride, a dual 5-alpha reductase inhibitor has been found to reduce bleeding from the prostate in a long term by inhibition of angiogenesis, and by apoptosis and has been used preoperatively to reduce bleeding that occurs during prostatectomy. Would the drug be effective in the control of acute haematuria of prostatic origin and so be used as a preliminary mode oftreatment? MATERIALS AND METHOD: Consecutive patients with gross haematuria were evaluated for the causes of haematuria. Seventy five of them identified to be of prostatic origin were further stratified as benign prostatic hyperplasia (BPH), or cancer of the prostate (CaP) based on clinical, biochemical and histologic evidence and randomized to 0.5mg dutasteride and normal saline irrigation on one arm and normal saline irrigation only as control, on the other arm. The time taken for haematuria to stop, the volume of irrigation fluid used, the number of patients that had recurrence, the number of patients transfused, the units of blood transfused and the number of patients that required surgery before haematuria stopped were recorded on both arms. Statistical analysis was done using SPSS version 20.0. RESULTS: Of the 75 cases, 49 (65.3%) had BPH while 26 (34.7%) had CaP. Twenty five (51%) of the 49 patients with BPH had normal saline irrigation only while 24 (49%) had dutasteride in addition to normal saline irrigation. Fourteen (53.3%) of 26 patients with CaP had normal saline irrigation while 12 (46.2%) had dutasteride in addition to normal saline irrigation. Haematuria took a significantly shorter time to stop in those that had 0.5mg dutasteride (4.9 days) than those who had only normal saline irrigation(8.0 days)(p=0.001). Volume of irrigation fluid used was also significantly less in those that had dutasteride than in those who had only normal saline irrigation (10 litres and 21 litres respectively) for BPH patients (p=0.008) and 8 litres and 17 litres respectively for CaP patients ( p= 0.000). Inclusion of dutasteride did not however significantly reduce the need for surgery. CONCLUSION: The result of this study shows that addition of oral dutasteride 0.5mg to normal saline irrigation is effective as a preliminary mode of treatment for cases of gross heamaturia caused by BPH and CaP. KEYWORDS: Haematuria, prostate, benign prostatic hyperplasia, adenocarcinoma of prostate, normal saline irrigation, dutasteride