The sensitivity of domestic and different sorts of synanthropic free living fowl to M. avium and pathogenesis of tuberculous process were observed by experimental infections. The partridge, domestic fowl, pheasant and sparrow were the most sensitive to intramuscular infection by suspension of M. avium. The sparrow, domestic fowl, laughing gull were the most sensitive to peroral infection by food contaminated by tbc poultry liver. After free contact between the poultry, the domestic fowl was the most sensitive to infection and then the sparrow, turkey, guinea fowl, pheasant and partridge were sensitive, too. The tuberculous lesions were observed in majority of infected fowls in cases of guinea fowl, turkey, laughing gull, domestic fowl, sparrow, partridge and pheasant after all types of infections. The pigeon, rook and turtle-dove were very resistant to M. avium infection. The largest quantities of mycobacteria in tissues of infected fowl were found in sparrow and guinea fowl and then in domestic fowl, pheasant and partridge. From the results of patho-morphological and culture examinations, we can distribute the experimentally infected fowl in four groups: very sensitive-domestic fowl, sparrow, pheasant, partridge, laughing gull; little sensitive-guinea fowl, turkey; resistant-goose, duck; very resistant-pigeon, turtle-dove, rook. It is necessary to know that the sensitivity of these sorts of fowl can be affectable by conditions of experimental infection. If we want to criticize the epizootological importance of individual sorts of fowl as a source of M. avium, we must take into account their sensitivity to M. avium, pathogenesis of tuberculous process and their breeding or zoological specificities of individual sorts.