Safety and Efficacy of QD Versus BID Silodosin With Lower Urinary Tract Symptoms Suggestive of BPH

Inclusion Criteria: Patients who have been diagnosed with BPH through digital rectal exam or ultrasonographic findings and meet the following criteria. * Outpatients aged 50 or over * Patients with a total I-PSS score of 8 or higher and a QoL score of 3 or higher * Patients with a prostate volume measured by transabdominal ultrasonography, or TRUS of 20 ml or greater * Patients with a maximum urinary flow rate (Qmax\_) of 15ml/sec or below (whose a void urinary volume of 120ml or greater) Exclusion Criteria: * Patients with a residual urinary volume of 200ml or greater * Patients with a history of prostatectomy * Patients with a history of intrapelvic radiation therapy * Patients with a history of prostatic hyperthermia * Patients with prostate cancer or suspected prostate cancer * Patients with complications considered likely to affect urinary passing such as neurogenic bladder, bladder calculus and active urinary tract infection. UTI * Patients conducting self-catheterization * Patients with renal impairment (serum creatinine of 3.0 mg/dl or greater) * Patients with severe heptic disorders (hepatic insufficiency, cirrhosis, jaundice, hepatoma) or with a total bilirubin of 3.0mg/dL or greater or AST/ALT 2.5 times higher than normal level * Patients with history of severe arrhythmia, cardiac failure, cardiac infarction, unstable angina, cerebral infarction within 6 months * Patients with a history of an allergy to α-blockers * Patients with orthostatic hypotension at around screening visit * Patients with an experience of other investigational product treatments within 4 weeks form screening visit. * Patients with a PSA of 10 or over, Patients with tumor identified by a prostate biopsy with a PSA of 4 or over (For patients taking 5α-reductase inhibitors for more than 3 months are presumed to have double than their actual PSA levels.) * Patients who have taken unstable doses of antidepressants within the 3 months or who are expected to take unstable doses during the study * Patients who have taken alpha blockers within the 2 weeks from the start of the therapy * Patients who have taken unstable doses of 5α-reductase inhibitors within the 3 months from the start of the therapy or who are expected to take unstable doses during the study. * Patients disqualified by the investigator.