ARTICLE INFO ______________________________________________________________ ______________________Purpose: Urinary retention is one of the most common complications contributing to surgical procedures. Recent studies have shown the benefits of alpha-adrenergic blockers in preventing post-operative urinary retention (POUR). The aim of this prospective study was to compare the prophylactic effect of tamsulosin with placebo on postoperative urinary retention. Materials and Methods:In this randomized placebo controlled, clinical trial, 232 male patients aged 18 to 50 years old admitted to Razi University Hospital for varicocelectomy, inguinal herniorrhaphy, and scrotal surgery were randomly assigned to receive either three doses of 0.4mg tamsulosin (n = 118) or placebo (n = 114), 14 and 2 hours before, and 10 hours after surgery. Patients were closely monitored for the development of urinary retention 24 hours after surgical intervention. The primary endpoint was to investigate the effect of tamsulosin in prevention of post-operative urinary retention during the first 24 hours after surgical intervention. Collected data were analyzed using SPSS software version 18 and the P < 0.05 was considered statistically significant. Results: One hundred and eighteen patients were included in tamsulosin arm and 114 in placebo arm. POUR in patients who received tamsulosin was significantly lower than placebo, as 5.9% of the patients treated with tamsulosin and 21.1% placebo group, reported urinary retention following surgery (P = 0.001). No serious adverse effects were seen in both groups.Conclusions: This study suggests that short perioperative treatment with tamsulosin can reduce the incidence of urinary retention and the need for catheterization after varicocelectomy, inguinal herniorrhaphy, and scrotal surgery.