Oral administration of Mycobacterium paratuberculosis to 61 pigs resulted in the development of caseous lesions of the mesenteric lymph nodes in 27.9 % of the animals. Positive results were found by bacterioscopy in 31.1 %, by culture in 60.7 % and by histological examination in 42.6 % of the animals. Histological changes typical of infection with M. paratuberculosis were found in the ileum in eight pigs. These changes, which consisted of infiltrations with epithelioid cells, were usually limited to the Peyer patches, but in one case such infiltrations were also present in the propria mucosae, similarly as in paratuberculosis in cattle.