The bone mineral content was evaluated in 30 male subjects aged between 60 and 90 years using the relief of the percent cortical area (PCA) at the level of the second phalanx of the left-hand index finger, by Garn’s method. This was to evaluate the rate of bone loss with increasing age. Testosterone, androstenedione, estrone, 17β-estradiol plasma levels were determined in all subjects by the RIA method. 60% of our patients showed increased bone resorption (PCA < 55%); in these subjects testosterone and androstenedione plasma levels were significantly lower than in subjects not affected by osteoporosis. A positive linear correlation is evident between PCA and testosterone, androstenedione and estrone plasma levels. Thus, like in women, decline of gonadic function determines an increased bone resorption in men t