Two tuberculin-positive baboons in a primate colony were found to have grossly visible tuberculous lesions in the liver, spleen, lung, and mediastinal lymph nodes on necropsy. Results of histopathologic examination of the tissues showed granulomas with Langhans giant cells. An acid-fast organism was isolated from tissues of each baboon; the isolates were identified as Mycobacterium bovis by being negative for niacin production and nitrate reduction and by their susceptibility to thiophen-2-carbosylic acid hydrazide and to 5% glycerol.