The control of cancer is at once a major public health problem and a problem of fundamental biologic interest. As a result of technologic developments and new insights in the realm of molecular biology, new and important approaches to an understanding of neoplasia are now possible. Several aspects of neoplasia are clearly of microbiologic interest, including the role of viruses in the etiology of cancer, control of the immune response to tumor cells, and the susceptibility of tumor-bearing hosts to overwhelming infection as a result of immuno deficiency. Recent advances in these areas led us...