[Viral carcinogenesis]

A short overview of the history of tumor virology is given with respect to the special data of research in this field done by Arnold Graffi and his coworkers. The theory of viral etiology of tumors during the 75 years since its inauguration had to be proven by scientists fighting for the idea of viral agents being the cause of several types of cancer in animals and man. Today this theory is accepted; a series of human tumors is known as induced by viruses, too. Moreover, tumor viruses have increased our knowledge of mechanisms of malignant transformation and the discovery of one genes has opened new possibilities for analysis of the process of cancerogenesis.