This volume contains the text of the plenary lectures given by internationally recognized experts in the field of gametogenesis and endocrinology at the 10th European Workshop on Molecular and Cellular Endocrinology of the Testis. Topics include spermatogonial transplantation, germ stem cell biology, regulation of meiosis and spermiogenesis, growth factors, cell signaling and transduction, steriodogenesis, androgen-regulated genes, sperm activation and sperm factors active at fertilization. The present volume pays particular attention to the use of genetically manipulated animal models in the study of the regulation of spermatogenesis and testicular functions.