In this study, men 65 years of age or older with low serum testosterone and symptoms of hypoandrogenism received testosterone or placebo for a year. Testosterone had a moderate benefit in sexual function and some benefit in mood but no benefit in vitality or walking distance. Testosterone concentrations in men decrease with increasing age. 1 , 2 Many symptoms and conditions similar to those that are caused by low testosterone levels in men with pituitary or testicular disease become more common with increasing age. Such symptoms include decreases in mobility, sexual function, and energy. These parallels suggest that the lower testosterone levels in older men may contribute to these conditions. Previous trials of testosterone treatment in men 65 years of age or older, however, have yielded equivocal results. Although testosterone treatment consistently increased muscle mass and decreased fat mass, 3 , 4 effects on physical performance, 3 , 5 , 6 sexual function, . . .