Benign prostatic hyperplasia is considered a progressive disease intimately linked with aging. The long-term use of combination therapy with a 5-alpha-reductase inhibitor, together with an alpha blocker in men with moderate-severe symptoms, reduces the risk of clinical progression and BPH-related surgery. It is unclear what the impact is of preoperative therapy with 5-ARI in patients that undergo surgery. The aim of our study was to evaluate the impact of preoperative therapy with 5-alpha-reductase inhibitors on: a) indication on the type of surgery; b) surgical and functional outcomes; c) surgical complications. This is a prospective observational study. It will include all patients undergoing surgery by TURP or Open Prostatectomy in a period of 24 months. We expect results that demonstrate significant and favorable influence of pretreatment with 5-alpha-reductase inhibitors on certain outcomes. Therefore, therapy with 5-ARI could be considered as neoadjuvant to surgery, whatever this is.