Currently, the only FDA-approved drug for testosterone in women is Estratest, which contains methyl testosterone, a compound that when given orally is associated with liver toxicity in animals and humans. Until recently, most hypogonadal men received biweekly intramuscular injections of testosterone. This regimen gives variable serum testosterone levels depending on the time of the blood sampling compared to the time of injection. Many male hypogonadal patients now receive their testosterone replacement via either transdermal testosterone gel or patch, with much more uniform serum testosterone levels. We have chosen transdermal testosterone gel for use in this study for several reasons: