This research attempts to address the problem of high prebalance of infectious disease in intensively managed pigs from the perspective of variable host immune responses as probable determinants of relative susceptibility and resistance to various agents of disease. The study was carried out by tests on the effects of the immune response regulating cytokine, interferon. Treatments were given in the first 7 days of a pigs life. Treatments were assessed on inductions of active immune responses to two test antigens, hen egg whites and killed candida. Effects on experimentally induced food allergy to the major egg allergen ovomucoid were also determined. Interferon given by intramuscular injection on days 1-7 of age enhanced rate of gain over the period 7-38 days of age. Immune response as measured by skin test reactions and serum antibody to egg whites and killed candida were variable by litter and individual. It had no effect on skin test response to killed candida when data were analyzed from individual litters but enhanced reactivity was suggested in pooled litter data.