INTERFERONS are glycoproteins which are synthesised by various vertebrate cells in response to virus infection or some other stimuli. They are secreted and then interact with other cells and convert these into an antiviral state, in which the multiplication of viruses is impaired¹. It is thought that transcription and translation are required for the establishment of the antiviral state as actinomycin D or inhibitors of protein synthesis, suitably administered, prevent or delay the effect^2,3. Results with enucleated cells also support this idea⁴. We show here that treatment of Ehrlich ascites tumour (EAT) cells with highly purified interferon results in the accumulation of a particular mRNA and the corresponding protein within the cells. However, we have not yet identified the function of the induced protein.