The Epstein-Barr virus was discovered 15 years ago. Since that time an immense body of information has been accumu lated on this agent which has come to assume great signifi cance in many different fields of biological science. Thus, the virus has very special relevance in human medicine and oncology, in tumor virology, in immunology, and in mole cular virology, since it is the cause of infectious mononu cleosis and also the first human cancer virus, etiologically related to endemic Burkitt's lymphoma and probably to nasopharyngeal carcinoma. In addition, continuous human lymphoid cell lines...