Several parameters of the biology of cancer of the prostate have been reviewed with a continuing assessment of the possible etiologic role of virus. These aspects include epidemiology, clinical studies, morphology, pathology, enzymology, immunology, endocrinology, model animal studies, in vitro systems, and viral investigations. From available literature it is concluded that, to date, the association with several urogenital tissues of herpes-type viruses has been best documented. It is suggested that a fundamental barrier to more sophisticated virologic and biologic studies is the lack of long term cell cultures of normal and pathologic prostate epithelium from males of all ages.