5ARIs are recommended for men who have moderate-to-severe lower urinary tract symptoms (LUTS) and benign prostatic enlargement (BPE) secondary to benign prostatic hyperplasia. Studies have confirmed the utility of combining 5ARIs with alpha-blockers; the MTOPS study showed that risk of overall clinical progression was significantly reduced after 4.5 years with combination therapy (finasteride/doxazosin) in comparison with either monotherapy, while the ongoing Comb AT trial (dutasteride/tamsulosin) has for the first time shown benefit in improving symptoms for combination therapy over monotherapies within 12 months of treatment. Data also suggest roles for 5ARIs in prostate cancer. Several studies indicate that treatment with a 5ARI improves the performance of PSA testing for identifying men with prostate cancer, while the PCPT showed a significant reduction in the risk of developing prostate cancer with finasteride. However, widespread use of finasteride in this setting has been tempered by an apparent increase in high-grade disease observed in the study. The ongoing REDUCE study will provide further insight into prostate cancer prevention with 5ARIs. 5ARI-containing regimens may have utility as less aggressive treatment options for patients who only have rising PSA after definitive local therapy, and in patients with disease resistant to androgen deprivation therapy who have PSA progression. Current evidence therefore shows that 5ARIs are effective in treating LUTS/BPE and preventing disease progression, and may also have a role in the prevention of prostate cancer. The overlap between BPE and prostate cancer may allow a more unified approach to managing these conditions, with 5ARIs having a central role. Prostate 69: 895-907, 2009.