Amounts of the proteins encoded by the two oncogenes c-myc and c-fos have been compared in seven specimens of hepatocellular carcinoma and two normal liver samples using a Western blot procedure. It was found that with the exception of one tumour, the amount of these proteins was markedly increased in the tumours when compared to the normal specimens. Furthermore, there appeared to be elevated c-myc and c-fos mRNA concentrations in the tumours which correlated with the protein levels. This is the first report of such a correlation in human hepatocellular carcinoma. We propose that transactivation of these oncogenes may in part be responsible for transformation in hepatocellular carcinoma.