The efficient induction of interferons alpha and beta (IFN-alpha/beta) in virus-infected cells is central to the antiviral response of a host and is regulated mainly at the level of gene transcription. Once produced, IFN-alpha/beta transmit signals to the cell interior via a specific receptor complex to induce an antiviral response. Recently, the auto-amplification mechanism of the IFN-alpha/beta system that follows viral infection has been identified. This mechanism is mediated by transcription factors of the IFN regulatory factor family and, in fact, may have evolved to render the system more robust in antiviral responses.