Transmissible gastro-enteritis is a virus-caused diarrhoeal disease of swine which may result in up to a total loss among newborn animals. Changes are, primarily, of pathologicoanatomic nature and take place in the small intestine. The epithelium of the intestinal villi is completely destroyed, and diarrhoea is the result. Deformation in blood composition is a secondary sequel. The diarrhoea proper causes dehydration and acidosis which, in conjunction with abnormal heart function due to hyperkalaemia, cause death of the piglets affected. Reference is made to the intrinsic immunological conditions in swine, and possibilities are discussed for immunoprophylactic control of transmissible gastro-enteritis by induction of effective lactogenic immunity. The approaches taken to vaccine application should largely correspond to the natural route of infection.