Recently, Interferon (IFN) beta has been reported to induce on HPK-IA cell line, an unusually marked cytopathic effect. Surprisingly this effect is not shared with IFN alpha. The morphological aspect of this cytopathic effect recals the one induced by highly cytopathic viruses. It has an induction time of less then four hours, may be inhibited by protein synthesis inhibitors and has a characteristic protein SDS-PAGE pattern. RT-PCR analysis has shown that IFN beta, but not alpha or gamma, reduces the transcription level of E6/E7 viral mRNA. Taken together these data suggest that cells may finely discriminate between IFN alpha and beta. Regarding HPK-IA cells this discrimination allows the activation of a specific transduction pathway ultimately leading to cell death. Cell death may be due to the concomitant severe reduction of E6/E7 viral transcription observed.