Cats are quite resistant to infection with Mycobacterium tuberculosis but are susceptible to M bovis, M avium complex, or M microti. M lepraemurium has been isolated from granulomatous lesions in the skin. Some unclassified acid-fast bacilli have also been isolated. Contaminated milk causing GI tract lesions, typically in the mesenteric lymph nodes, is the most common circumstance, and historically this was responsible for a very high percentage of tuberculous cats in Europe. Rapid, hematogenous dissemination to other organs, including the lungs and regional lymph nodes, can occur. Infected skin or deeper wounds sometimes give rise to tuberculous sinuses. Lesions have a central area of necrosis, usually without calcification. The tuberculin skin test is considered unreliable in cats. Diagnosis may be assisted by radiography and ELISA. Identification of the organism is necessary to confirm a diagnosis. Efficacious treatment protocols are not available. Therefore, it is recommended that cats infected with M bovis be euthanized because of public health concerns.