Androgen replacement therapy for ED is indicated only in clearly demonstrated hypogonadism and/or low testosterone levels. The results of androgen replacement in ED are frequently not very satisfactory—even in young men with low testosterone levels, improvement during testosterone replacement may be marginal (Althof and Seftel 1995). Administration of testosterone in healthy men with ED is not effective (Schiavi et al. 1997). Androgen replacement in hypogonadism is usually lifelong. In the U.S., testosterone is available in oral (Testred), intramuscular (Delaestryl), and transdermal (Androderm Transdermal System, or Androgel) preparations. The side effects and complications of androgen replacement (e.g., prostate cancer, breast cancer, liver toxicity, hyperlipidemia, cardiovascular side effects, sleep apnea) were discussed earlier, in the section on male hypoactive sexual disorder.