Objective: To evaluate the efficacy of tamsulosin compared to placebo for treating catheterized patients with acute urinary retention (AUR) caused by benign prostatic hyperplasia (BPH), by comparing the numbers of patients who voided successfully after removing their catheter after 3 days with those in which catheter removed after 7 days. Patients And Methods: This is a prospective randomized study, Men with AUR secondary to BPH were catheterized and then, if they fulfilled the entry criteria, were randomly assigned to receive 0.4 mg tamsulosin hydrochloride for three days or seven days, After that the catheter was removed and the ability to void unaided assessed. Results: In all, 50 men (mean age 60.4 years) were randomly assigned to receive tamsulosin for 3 days (25 patient) or for 7 days (25paient). sixteen men taking tamsulosin for 3 day and nineteen patient taking tamsulosin for 7 days did not require re-catheterization on the day of the trial without catheter (64% and 76% respectively, P = 0.538). Complications as urinary tract infection, urine leakage, haematuria or catheter obstruction occurred in four (16%) men who received tamsulosin for three days, and twelve (48%) men who received tamsulosin for seven days (P = 0.032), but overall the incidence of complications of tamsulosin was comparable in the two groups. Conclusion: Men catheterized for AUR can void more successfully after catheter removal if treated with tamsulosin, and are less likely to need re-catheterization. But the complications were increased with period of catheterization.