The papers in this volume were presented at the Symposium held March 24-26, 1980, at the Worcester Foundation for Experimental Biology, Shrewsbury, MA. The meeting was organized to review recent advances in basic and clinical research work on hormone-responsive tumors of the reproductive system. The association between protracted hormone action and cancer of the reproductive system is now irrefutable. Yet we still do not know how hormones initiate and promote neoplastic transformation of their target cells. A major effort is currently being directed at understanding the hormonal regulation of neoplastic cells, especially those arising from the breast, uterus, pituitary gland and prostate. The symposium brought together leading experts whose research is focused on this important area of human health. Although many questions remain to be answered by future studies, the material covered in this volume provides an up-to-date overview of the current status of work in this area. The subjects range from the mechanism of hormone action to the treatment of hormone-dependent tumors, and topics include estrogen, progestin, androgen and glucocorticoid action; hormone receptors; specific protein responses; developmental effects of estrogens and antiestrogens; the DES syndrome; regulation of the cell cycle; therapeutic effects of antiestrogens, aromatase inhibitors, iodoestrogens, progestins on estrogen dependent tumors; characterization of retinoid-binding sites; and the utility of various tumor markers. Our intent was to synthesize current information from basic and applied studies in the hope that this might clarify controversial areas and provide added impetus to the search for new approaches to cancer control. Although this book is intended primarily for oncologists, endocrinologists and cancer biologists, it is directed to all scientists and students with an interest in carcinogenesis.