Breast cancer continues to be a major problem. In Volume 1 of this series we dealt exclusively with topics concerned with therapy. In Volume 2 we explored various aspects of experimental biology which are critical to our developing better methods of diagnosis and treatment. In the pres­ ent volume, we tum to a series of individual topics of considerable interest, including systemic methods for hormonal ablation, screening for early cancer, male breast cancer, and more. The first chapter addresses the question of why some breast tumors metastasize and others do not. Based on elegant animal tumor models, Kim believes that metastasizing tumor cells are the undesirable by­ product of the host immune surveillance mechanism. Unstable mem­ brane structures lead to shedding of membrane constituents, abnormal locomotive properties, and evasion of the host defense system. Factors which alter membrane structure will therefore have to be considered in our approach to the management of early breast cancer.