 Only 10% mortality rate was observed in C57BL/6 mice after the administration of very high virulent dose of 1*105 TCID50.It was shown that resistance to the lethal effects of Sendai virus in mice is genetically controlled and expressed through control of viral replication within the first 72 hours of infection.Treatment of both strains with exogenous IFN before and during viral infection led to an increase in survival time in C57BL/6 mice, but all animals of both strains ultimately succumb to SeV caused disease.