[Oncogene].

Retroviruses have long been fascinating to biologists because of their capacity to induce neoplasms in various animals. The transformation of the cells by the viruses was due to their oncogene-products. The viral oncogenes were thought to be originated from DNA of normal cells by recombination events between retroviruses and cellular oncogenes. Recently, many cellular oncogenes were identified in human cancerous cells by the DNA transfection method, some of which were found to contain sequences related with already known viral oncogenes. On the other hand, the research on the relation between these oncogenes and chromosomal translocation associated with carcinogenesis is now in progress.