Infection with the human immunodeficiency virus (HIV) and human T-cell lymphotropic virus type I (HTLV-I) is known to be associated with an increased risk of neoplastic disorders, especially Kaposi's sarcoma and aggressive B-cell lymphoma for the former, and T-cell lymphoma for the latter. The information obtained from the study of these infections has led to remarkable advances in our understanding of the immune system, as well as the biology of human neoplasms. The management of malignant diseases in such patients also poses substantial challenges to clinicians. This book provides an overview of the epidemiology, biology, clinical features, and clinical management of neoplasms occurring in such individuals. It is an important resource for clinicians treating these diseases, and for basic scientists who have an interest in this field.