Amplification and expression of myc-related oncogenes were studied on adenovirus-induced tumors (D and IC) and spontaneous hapatoma (P), all of which had been successively trans-planted in C3Hf/OK mice. c-myc expression waas elevated in the D, IC anf P tumors, and a 8.9-fold amplification of c-myc was observed in the IC tumor. In the D tumor N-myc expression was elevated and a 1.9-fold amplification of N-myc was also observed. Amplification of c-myc in the IC tumor was suspected to be a result of selection for c-myc amplified cells during successive transplantation. Although expression of genes, c-myc, N-myc and E1A of adenovir-us, suppress each other, the results of this experiment, especially elevated expression of N-myc and c-myc in the D tumor, implicated deregulation of myc family genes in malignancies indiced by adenovirus.