A well characterized human hepatocellular carcinoma cell line (PLC/PRF/5) containing complete sequences of HBV-DNA in integrated form into host DNA and growing under serum-free conditions was used to test the effect of human growth hormone (hGH) on the expression of the integrated viral DNA. Data in our hands point to an early, specific effect of hGH on HBV-DNA integrated sequences which appears to be unrelated to the late effect on total protein synthesis. Moreover this approach enabled us to detect specific hGH receptors on the cell membrane of PLC/PRF/5 cell line.