We performed a post hoc analysis of data from phase 3 and 4 studies to evaluate the efficacy of silodosin 8mg in patients with severe lower urinary tract symptoms (LUTS) related to benign prostatic obstruction (BPO). The presence of two or more of the following criteria was adopted to define severity: total International Prostate Symptom Score (IPSS) 20-35, quality of life (QoL) score 5-6, maximum urinary flow <5ml/s or postvoid residual volume ≥100ml, and prostate volume ≥50ml. Mean improvements in total (8.1 vs 4.7), storage (3.1 vs 2.0), voiding (5.0 vs 2.7), and QoL (1.3 vs 0.7) IPSS scores were significantly greater for patients receiving silodosin compared to placebo (all p< 0.0001). Mean improvements in total, storage, voiding, and QoL IPSS scores were similar for the severe and not severe LUTS cohorts. In conclusion, silodosin significantly improves symptoms and QoL in all LUTS/BPO patients, including those with severe symptoms. PATIENT SUMMARY: Silodosin improves symptoms and quality of life for patients with severe lower urinary tract symptoms related to benign prostatic obstruction.Copyright © 2020. Published by Elsevier B.V.