PIP: The use of a specific radiolabeled antiglobulin test to detect antisperm antibodies has given positive results in 7% of infertile men and 13% of infertile women, and may be a reliable means of identifying and possibly treating patients whose infertility is caused by immune mechanisms. The importance of studying the infertile couple rather than the women only has been emphasized; the sparse data available suggest that deficiencies may occur in the man in as many as 1/2 of the estimated 10-15% of couples who are infertile. Most infertile men are still classified as having idiopathic oligospermia, implying sperm counts below those associated with ready fertility, without apparent cause. It is now clear that the fertility potential of both partners must be evaluated in assessing the importance of oligospermia, making assessment of the response to therapy more difficult. The diagnosis of oligospermia itself is beset by such difficulties as the variability of the sperm count at both normal and low levels and the overlap between presumed fertile and infertile levels of sperm. The maximum number of sperm necessary to define oligospermia has declined over recent years to 10 million sperm/ml. Oligospermia appears to represent a common response of the male reproductive system to a variety of insults. Most patients have abnormal pituitary responsiveness related to decreased feedback control of hypothalamus and pituitary by the testis. Altered testicular function is most likely when the sperm count is below 5 million/ml. Environmental factors, intrinsic testicular defects, and androgen insensitivity due to a decreased number of androgen receptors are other possible causes. The probable diversity of pathogenesis and the difficulty of obtaining properly controlled studies are reasons for the inconclusive results of most therapeutic efforts. However, significant progress in the understanding of testicular disorders in the past few years has led to an outburst of scientific and collegial activities related to andrology, and there is reasonable hope for a more definite understanding of male fertility in the near future.