In calves at the age of 2—3 months experimentally infected with BHV-1 clinical signs, humoral and cellular responses and the intensity of delayed skin hipersensitivity were examined. The examinations were performed from 3 to 56 day post infection, e.g. at early period of infection. It was found that apart from typical clinical signs and humoral response to BHV-1 infection, cellular immune response measured by the test of blastic transformation of leukocytes appeared by about 7 days before humoral immune response and that it persists only up to the day 21 post infection. In the leukocyte migration tests, leukocyte inhibition was noted at the day 7 and from that day since the end of observation acceleration of leukocyte migration was noted. A delayed skin hipersensitivity measured by allergic skin test appeared between day 21 and 28 post infection.