Andrology, a counterpart to gynecology, deals with the study of the male reproductive organs. Clinical andrology has been neglected primarily because of the lack of relevant, accurate laboratory methods for functional analysis, but in the last decade substantial progress has been made in the understanding of male reproductive biology. This progress has resulted from modern tech- niques and instrumentation in microanatomy, immunology, neurophysiology, pathology, genetics, endocrinology, biochemistry, biophysics, urology and surgery. These studies are scattered in such a wide spectrum of journals that andrologists can hardly keep abreast of the advances. There have been numerous textbooks on the testes, male accessory organs and semen but the clinical aspects of andrology have not received similar emphasis. Since literature concerning clinical andrology is extensive and widely scattered in many different publica- tions, we hope that a useful purpose will be served by summarizing the more pertinent material in a series of volumes which can be made readily available to students of andrology. It was decided that a series of specialized monographs should be devoted to clinics in andrology. These ten volumes of the series are an attempt to coordinate anatomical, physiological, biochemical, endocrinological, pharmacological and immunological aspects of the spermatozoa, testes, epi- didymis and other accessory genital organs. Little is known about the effect of diet, diseases, environmental factors and drugs on male reproduction. The interest in developing new male contraceptive methods will stimulate research in andrology.