This volume, Biological and Hormonal Therapies of Cancer, which is part of the series Cancer Treatment and Research, presents selected new information concerning biologic and hormonal therapy of cancer. We have attempted to provide the reader with topics of major interest in a timely fashion. There is renewed interest in biologic therapy of cancer. Two chapters review the role of interferon in the hematologic malignancies and in solid tumors. Vaccine therapies have come to the forefront of cancer therapy re cently, and two chapters approach different strategies of vaccine therapies; one reviews the cellular vaccine therapies and another the anti-idiotype ap proach. The hormonal therapy chapters focus on current uses of endocrine therapy in endometrial, breast, and prostate cancer. In addition, hormonal strategies for the prevention of breast cancer and endometrial cancer, including excit ing information relating to phytochemicals, are presented. The effects of tamoxifen on endometrium is a topic of major interest and is discussed in detail. Finally, there is a chapter on estrogen receptor expression and regula tion in human breast cancer. These chapters are all written by experts in the field and contain timely and relevant information of interest to laboratory and clinical scientists and practitioners alike. Biologic and endocrine therapies represent major areas of cancer research interest. The advent of newer biologic therapies, including new antibody targeted treatments, and the use of biologics as tumor modulators to enhance the effects of other treatment regimens is an exploding avenue of research.