The occurrence and expansion of avian mycobacteriosis in the pigeon, its sensitivity to infection and epizootological importance as a source of M. avium were investigated. A total of 470 pigeons were examined coming from seven localities with different epizootological situation in avian tuberculosis. Tuberculous lesions were found out in 2 birds (0.43%) and mycobacteria were isolated from five birds (1.06%). Four out of the five isolated strains of mycobacteria were pathogenic to the domestic fowl. Experimental infections demonstrated the pigeon's high resistance to M. avium. Intramuscular infection with the suspension of M. avium induced histological lesions in the muscle at the spot of puncture in a fortnight, in the liver it was in 28 days, in the lungs and intestines in 56 days. Macroscopic changes were observed at the spot of puncture only in 21 days, but they were not observed in other organs and tissues. The mycobacteria were isolated since the 12th day after infection, particularly from the muscle at the spot of puncture, from liver, spleen and medulla. Macroscopic changes were found out in the intestine in 160 days after peroral infection with feed contaminated with the liver of tuberculous fowl. The mycobacteria of various organs and tissues were isolated from the pigeons killed in 160 days. After a contact with the tuberculous fowl histological changes in the intestinal wall were observed in 380 days in one case only and the mycobacteria were demonstrated by cultivation in the medulla of a pigeon which died in 68 days.