The 5α-reductase inhibitor dutasteride and the α(1)-adrenergic receptor antagonist tamsulosin are available as a fixed-dose combination for use in men with symptomatic benign prostatic hyperplasia (BPH) and an enlarged prostate. Dutasteride 0.5 mg/day plus tamsulosin 0.4 mg/day improved lower urinary tract symptoms (LUTS) to a significantly greater extent than dutasteride or tamsulosin alone in men with BPH, moderate to severe LUTS and an increased risk of disease progression, according to the results of the randomized, double-blind, multinational CombAT trial. The mean change from baseline in the total International Prostate Symptom Score was significantly greater with dutasteride plus tamsulosin than with dutasteride or tamsulosin alone after 2 years (primary endpoint) and 4 years of therapy. After 4 years' therapy in the CombAT trial, the time to first acute urinary retention or BPH-related surgery (primary endpoint) significantly favoured men with symptomatic BPH who were receiving dutasteride plus tamsulosin versus those receiving tamsulosin alone, with no significant difference between recipients of dutasteride plus tamsulosin and recipients of dutasteride alone. In the CombAT trial, health-related quality of life and treatment satisfaction were improved to a significantly greater extent with dutasteride plus tamsulosin than with dutasteride or tamsulosin alone. Combination therapy with oral dutasteride plus tamsulosin was generally well tolerated in patients with symptomatic BPH in the CombAT trial.