Authoritative researchers and clinicians review our latest understanding of andrology in both basic science and clinical medicine. Topics range from explaining the biology of androgens-from several different perspectives-to illuminating their role in the development and modulation of physiologic systems. Authors demonstrate in a number of cases that testosterone can be a useful adjunct to the treatment of a variety of disease states. Other chapters consider important topics such as androgens use in athletes, the potential of androgens to improve physical function and quality of life in older men, and androgens as potential male contraceptives.