Introduction: Lower urinary tract symptoms (LUTS) due to benign prostatic hyperplasia (BPH) are common among older men. Beside watchful waiting and surgery, medical therapy includes alpha adrenergic blockers, 5 alpha reductase inhibitors, and phytotherapy. Alpha blockers are considered to be the main treatment for BPH-associated LUTS depending on the evidence that prostatic smooth muscle contraction is responsible for bladder outlet obstruction via alpha adrenergic receptor-mediated mechanism. Tamsulosin is a super selective alpha blocker. Improvement of LUTS can be assessed by maximum flow rate (Qmax), average flow rate (Qavg), post void residual (PVR) urine volume and international prostate symptom score questionnaire (IPSS). Objectives: To compare the efficacy and the safety of Tamsulosin 0.4mg/day and 0.8mg/day in patients suffering from lower urinary tract symptoms due to benign prostatic hyperplasia. Patients and Methods: A Prospective Interventional, double-blinded, controlled study was carried out on 93 patients who met the criteria and divided randomly into 2 groups; group A for Tamsulosin 0.4mg/day and group B for Tamsulosin 0.8mg/day. International prostate symptom score, Post void residual urine volume, and maximum flow rate of urine were assessed before and after 4 weeks of treatment. Results: Both study groups showed a significant reduction in storage sub-score but only frequency was significantly reduced in group B (P < 0.001). On the other hand, Tamsulosin 0.8 mg was superior to Tamsulosin 0.4 mg regarding voiding sub score except for straining (P = 0.325). Accordingly, the total international prostate symptom score was significantly improved in group B (P < 0.001). Furthermore, maximum flow rate and post-void residual urine volume were notably improved with Tamsulosin 0.8 mg compared to Tamsulosin 0.4 mg (P < 0.001). Although the adverse events; such as headache, orthostatic hypotension, and retrograde ejaculation were more frequent, but not significant, to occur with Tamsulosin 0.8 mg, only dizziness was noted to be significant. Conclusion: Tamsulosin 0.8 mg has shown better outcomes in treating patients who suffer from lower urinary tract symptoms due to benign prostatic hyperplasia than Tamsulosin 0.4 mg, and besides that, it is well tolerated. [ABSTRACT FROM AUTHOR]