The conditions of delayed-type hypersensitivity induction following immunization with an inactivated influenza vaccine in BALB/c and CBA/H mice treated with cyclophosphane were studied. The results showed that the delayed-type hypersensitivity reaction had no type specificity when revealing preparation injected to immunized mice is a vaccine prepared with chorioallantoic fluid, but it is specific when a tissue vaccine is used. The use of inactivated influenza viruses cultivated on different cell-types for sensitization and revelation of the hypersensitivity state allowed to evaluate the level of the delayed-type hypersensitivity induced by untreated virus.