['To determine the differences in efficacy between therapy using IFN-beta and ribavirin, and using IFN-alpha and ribavirin.', 'We studied the effect of combination therapy consisting of IFN-beta and ribavirin on mouse hepatitis virus (MHV) infection in mice.', 'Combination treatment of ribavirin and IFN-alpha was more effective than IFN-alpha mono-treatment in the MHV-mouse system, and combination treatment with ribavirin and IFN-beta was more effective than IFN-beta mono-treatment in the MHV-mouse system. Furthermore, administering IFN-beta once or twice one day before combination treatment using ribavirin and IFN-alpha was more effective than administering IFN-alpha once or twice one day before the combination treatment using ribavirin and IFN-alpha.'] Does the combination of type I interferon and ribavirin have an inhibitory effect on mouse hepatitis virus infection?