Changes in nuclear phenotypes and DNA amounts in GBK cells with advancing infection caused by Aujeszky's disease virus (ADV) and bovine diarrhoea virus (BDV) were studied. The purpose was to determine whether changes in patterns of chromatin supraorganization and DNA amounts varied with advancing RNA and DNA viral infections in a mammalian cell line, similar to changes observed in transformed cells or cells subjected to other stress agents. Discernible changes were seen only 6 h after infection by either virus. Changes not only in DNA amounts but also in chromatin supraorganization, differing from those reported for transformed cells or cells subjected to other stress agents, were found in the infected cells. Polyploidy was demonstrated irrespective of the viral infections. The viral DNA may have contributed to DNA values in interphase nuclei of ADV-infected GBK cell.95379111121