Benign prostatic hyperplasia (BPH) is a complex and progressive disease common in aging men. While associated with bothersome lower urinary tract symptoms, it may also result in additional serious complications such as refractory hematuria, acute urinary retention, and BPH-related surgery. Medical therapy has been offered as an approach to halt this progression and perhaps reverse the pathophysiology of BPH. While alpha-blockers provide rapid relief in the form of improved flow rate, their effects may not reduce the overall risk of BPH-related complications. 5α-reductase inhibitors were therefore introduced to affect the underlying disease process by inhibiting the enzyme which converts testosterone to dihydrotesterone, the primary androgen involved in normal and abnormal prostate growth. Through this inhibition, prostate size is decreased, thereby reducing the risk of acute urinary retention and BPH-related surgery while providing symptom control. These effects are most pronounced in men with enlarged prostates (>25 mL) who are at the greatest risk of disease progression. This article reviews the literature for finasteride used in the treatment of BPH and provides evidence for its efficacy, safety and tolerability, applicability for combination therapy, and considerations of its effects on prostate cancer risk.