The spread of HSV of type 1 and 2 was investigated after intraperitoneal, intraplantar and intracerebral infections of resistant (C57/bl) and susceptible (NMRI) mice. The virus spreads after i.p. infection to the spleen and the liver to the same extent in both strains of mice. However, virus is eliminated earlier in resistant mice. Intracerebral infections revealed a peculiar type of resistance of C57/bl mice especially for type 2 of HSV. HSV multiplies in the thymus at the early stage of infection and can be detected in this organ in sick mice of NMRI strain. HSV-1 and 2 can be detected in the spinal cord of C57/bl mice without sickness or death of these animals.