During the past decade extensive investigations have been done on the testis. Since the observations have been published in many different journals. it seemed appropriate to bring together and summarize some of the pertinent findings in a single volume. Twenty-eight scientists and clinicians from nine countries have contributed to this book. They have reviewed the literature and presented their own new observations on the developmentaL anatomicaL physiologicaL biochemical and pathological aspects of the descended and cryptorchid testis. In addition several contributors have evaluated the usefulness of certain animals as models for systematically studying specific aspects of cryptorchidism. It is hoped that this volume will serve as a useful summary and reference for those working in this area and that it will encourage further research in testicular physiopathology. The editor thanks the contributors for their enthusiasm cooperation and meticulous writing of the chapters. The support of the Departments of GynecologyjObstetrics and the Department of Physiology of Wayne State University School of Medicine. Detroit and the assistance from the staff of Martinus Nijhoff are gratefully acknowledged. The cheerful cooperation of Miss Lori Rust and Miss Penny Stoops who helped to type and assemble the volume is most deeply appreciated.