During the past twenty years many meetings concerning the reproductive process have taken place. Both structure and function of female and male gonads have been major topics at these gatherings. However, in only a few instances has the male gonad, particularly the human, been the main subject of discussion. This Conference was designed to focus attention on the human testis. A group of investigators representing various scientific disciplines was invited to this Workshop to discuss this subject from a morphologic,physiologic, biochemical, genetic and pathologic point of view. In some areas, especially that related to embryology, basic human data are lacking, thus relevant animal studies were also presented. Effort was made in these comparative studies to illuminate rather than complicate the understanding of fundamental phenomena in human reproductive physiology.This volume contains the Proceedings of this Workshop which served as a forum for interexchange of ideas which have enriched our knowledge of the human testis. If the topics discussed excited our interest for further research and have opened new and original lines of study, then the organization of this gathering was amply justified.