The diabetogenic variant of encephalomyocarditis virus (EMC-D) induces a diabetes-like syndrome in certain strains of mice. A study was done to determine if virus-induced diabetes could be prevented by interferon (IFN). It was found that the production of diabetes by EMC-D was blocked by either IFN beta or a variety of IFN-inducers in SWR/J, but not ICR Swiss mice. The replication of EMC-D in cell culture was inhibited by IFN beta. It is concluded that the response of pancreatic beta cells to the protective effect of IFN, is probably under genetic control.