We report a novel, unusually severe cytopathic effect of interferon-beta (IFN-beta). Data concerning antibody neutralization, induction and recovery time course, CPE50 dose, impact on oxidative metabolic activity and 1D SDS-PAGE total cellular protein analysis are provided for preliminary characterization. This cytopathic effect appears to be linked to human papillomavirus type 16 (HPV-16) genome presence as it is markedly evident in the HPV-16-immortalized HPK-IA cell line, but is not induced in diploid keratinocytes. It is also not induced in highly malignant SiHa cells suggesting that it also requires a fairly conserved phenotype. This effect is unexpectedly not shared by IFN-alpha pointing to a discrimination between IFN-alpha and -beta signal despite the well-known sharing of a common receptor. It remains to be clarified whether this divergence, undetectable in other cellular systems, represents a direct effect of viral presence or a non-specific consequence of cellular homoeostatic disregulation induced by the papillomavirus genome.