Viruses are the agent responsible for perhaps up to one million cases of cancer worldwide each year. Significantly, the study of viruses has also provided important clues to the causes and development of the most common human cancers. This volume presents an account of those viruses which have been directly associated with common human malignancies such as human papillomavirus (HPV), cervical carcinoma, Epstein-Barr virus (EBV) and Burkitt's lymphoma. In addition, the biology and biochemistry of those viruses which have been shown to be capable of transforming cells in culture are described in detail. Thus adenovirus are discussed, as are the other small DNA tumour viruses - Simian virus 40 (SV40) and polyoma virus. Consideration has also been given to human T-cell leukaemia virus (HTLV), hepatitis B virus (HBV) and human herpes virus 8 (HHV8), amongst others. General themes such as the host's immune response to viral infection, virally-induced apoptosis and the use of viruses as a delivery system in gene therapy have been discussed. Individual chapters have been written by an international group of experts in their own field of research.