Objective: Benign prostatic hyperplasia (BPH) is a nonmalignant enlargement of the prostate associated with aging. BPH can cause lower urinary tract syndrome (LUTS). Medical therapy for patients with moderate and severe LUTS symptoms comprises a-1 adrenergic receptor antagonists. This study aimed to determine whether there are differences in the international prostate symptom score (IPSS) and maximal flow rate (Qmax) of patients with BPH receiving either silodosin or tamsulosin over 12 w. Methods: This study was a double-blind randomized clinical trial. Subjects were 50 men aged ³ 50 y diagnosed with BPH with an IPSS ³ 8 at the Gatot Soebroto Indonesian Army Hospital. The participants received either silodosin or tamsulosin. Their IPSS and Qmax were assessed at the initial assessment and after 4, 8, and 12 w of treatment. Results: The initial median IPSS was 15 in the tamsulosin group and 17 in the silodosin group (P = 0.808). After 12 w of therapy, the median IPSS decreased to 9 in the tamsulosin group and 10 in the silodosin group (P = 0.186). The initial median Qmax was 10.1 ml/s in the tamsulosin group and 10.9 ml/s in the silodosin group (P = 0.290). After 12 w of therapy, the median Qmax increased to 12.1 ml/s in the tamsulosin group and 11.9 ml/s in the silodosin group (P = 0.969). Although the differences between groups were not significant, the initial and 12-week IPSS and Qmax values differed significantly within each group. Conclusion: There were no significant between-group differences in the IPSS or Qmax after 12 w of therapy. However, both silodosin and tamsulosin produced significant differences between initial and 12-week assessments of IPSS and Qmax.