The present report describes a case of chronic diarrhea with several ulcers in the ascending colon in a 47-year old woman who immigrated to Canada from the Philippines. A biopsy from affected colon revealed caseating granulomas and culture grew mycobacterium avium subspecies. Polymerase chain reaction from the colonic biopsy specimen confirmed the presence of mycobacterium avium subspecies that was subsequently identified by hsp65 sequence to be mycobacterium avium hominissuis (MAH). Anti-mycobacterial therapy was started but discontinued by the patient. After 6 months a repeat colonoscopy was macroscopically normal and no granulomas could be seen on biopsies taken from normal appearing colonic tissue. The epidemiological features, host-range and laboratory identification of this unusual organism are discussed.