The effects on sexual function (SF) by the drugs commonly used in the treatment of benign prostatic hyperplasia (BPH) and prostate cancer (PC) have been analyzed. BPH therapy: alpha-blockers have no adverse effects on SF; the only one without significant hypotensive effect, Tamsulosin, can cause retrograde ejaculation in 4–8% of cases. 5-Alpha-reductase (Finasteride and Dutasteride) inhibitors could have detrimental effects on erectile function, libido and ejaculation in a small percentage of cases rarely exceeding 10%; these effects are reversible and their incidence reduces after 1 yr. Phytotherapy (extracts from pygeum africanum and serenoa repens) and mepartricin have no unfavorable action on SF. PC therapy: Loss of erectile function and libido are the norm with the use of LH-RH analogues, estrogens and steroidal antiandrogens (cyproterone acetate). Non-steroidal antiandrogens (Flutamide, Bicalutamide and Nilutamide) allow the preservation of SF in two-thirds of cases.