Since prostate cancer becomes more common with age, at least one-third of men have sexual problems at diagnosis. All localized treatments for prostate cancer greatly increase the prevalence of sexual dysfunction, which include loss of desire, erectile dysfunction, and changes in orgasm. Even men on active surveillance have a higher rate of problems than matched peers without prostate cancer. However, men given androgen deprivation therapy (ADT) have the worst rates of sexual dysfunction. Even after 3 to 4 months of ADT, men's desire for sex is decreased and irreversible damage may occur to the erectile tissue in the penis. Erections do not recover in about one-half of men, even if ADT is discontinued. Although intermittent ADT allows some recovery of sexual function, serum testosterone requires 9 to 12 months off ADT to recover. Again, one-half of men have permanent erectile dysfunction. If ADT causes atrophy of the erectile tissue, blood leaks out of the venous system during erection. This syndrome is difficult to treat except with surgery to implant a penile prosthesis. Despite the high rate of sexual problems in men on ADT, a small group stays sexually active and is able to have reliable erections. To improve men's sexual satisfaction on ADT, it may be important to educate them about getting extra mental and physical sexual stimulation, as well as using penile rehabilitation during hormone therapy. Information on reaching orgasm and coping with problems such as dry orgasm, pain with orgasm, and urinary incontinence during sex also should be provided.