The influence of various doses of inactivated PI-3 virus vaccine on the serological response of guinea pigs and calves were studied. When testing vaccine in groups of guinea pigs revealed single dose 200 HA units elicited a response of 32 HI units, 400 HA units induced response 128 HI units, 600 HA units induced a response of 256 HI units after 14 days. This response was not improved by further increasing the dose of antigen on challenge all the vaccinated animals proved resistant but the controls developed pneumonia. The 3ml and 5ml dose of monovalent PI-3 and Combined inactivated respiratory virus vaccine (Pheumo-3) respectively gave better and higher immune response than the other studied dose (1 and 2ml) of monovalent PI-3 vaccine and 3, 10ml of Pheumo-3. Moreover, the amount of Alhydrogel which has tobe added to the vaccine as well as the validity and sterility of the vaccine were also examined.