PURPOSE: To evaluate efficacy and outcome of tamsulosin therapy for 4 mm-10 mm uncomplicated distal ureteral stones. MATERIALS AND METHODS: A total of 150 patients (adults with newly diagnosed single unilateral distal ureteral 4 mm-10 mm stones) were double blindly randomized into GA or GB. All patients received traditional treatment of hydration and analgesia as needed. Additionally, patients received either placebo (GA) or 0.4 mg tamsulosin (GB) oral tablets once daily. Treatment and follow up were continued for up to 4 weeks. Endpoints were spontaneous stone passage rates (SPR) and passage time for different stone sizes within 4 weeks study period. RESULTS: Analysis included 75 patients, in each group, with comparable characteristics. Overall SPR was 56% in GA and 81.3% in GB; achieving significant absolute risk reduction (ARR = 25.3%; p < 0.01) and number needed to treat (NNT) of 3.95. SPR for stones ≤ 6 mm was 69.2% in GA versus 90.7% in GB (ARR = 21.5%, p < 0.01). For stones 7 mm-10 mm, SPR was 26.1% in GA and 57.1% in GB (ARR = 31.0%, p <0.01). NNT for ≤ 6 mm and 7 mm-10 mm stones was 4.65 and 3.23, respectively (p < 0.05). Median time for passage of ≤ 6 mm stones was 17 versus 9 days in GA and GB; while for 7 mm-10 mm stones it was 20 versus 15 days, respectively. During the first two weeks, 77.8% of ≤ 6 mm stones in GB have passed versus 23.8% of 7 mm-10 mm stones. Analgesia consumption was significantly less in GB (p < 0.01). No significant adverse effects were observed. CONCLUSIONS: Tamsulosin therapy for uncomplicated distal ureteral calculi augments SPR, shortens passage time and decrease need for analgesia. Particularly, tamsulosin shortens the passage time for smaller stones, and augments the passage rate for larger stones.