The action of interferon1 as well as polypeptide hormones 2 has been shown to be transmissible between cells, possibly through gap-junctional transfer of secondary messenger molecules. This and other similarities between interferon and polypeptide hormones3 have led us to propose that there is a common cellular pathway of interferon and hormonal action. If correct, this hypothesis would predict that interferon should cause a species-specific hormonal response and a hormone should induce tissue-specific antiviral activity. If these two responses are mediated by similar secondary messengers, they should be transmissible and cross-activate cells. Here, we show that interferon caused a species-specific hormonal response (noradrenaline-like stimulation of the beat frequency of cultured mouse myocardial cells). Noradrenaline induced an interferon-like antiviral state in mouse myocardial cells but not human amnion (WISH) cells. In conditions which demonstrate interferon-induced transfer of viral resistance, exposure of co-cultures of mouse myocardial cells and WISH cells to either human interferon or noradrenaline caused an increased beat frequency in the myocardial cells and development of antiviral activity in WISH cells, respectively. These studies strongly suggest common pathways of interferon and hormonal stimulation that are transmissible between cells. © 1980 Nature Publishing Group.