This paper describes the identification of cultured mycobacteria with a panel of monoclonal antibodies directed against species-specific epitopes in a Western blot (WB) test and in an immunofluorescence test (IFT). In WB, we identified mycobacteria of the Mycobacterium tuberculosis complex (M. tuberculosis, M. africanum, M. bovis, M. bovis BCG, and M. microti) with 10(8) bacteria. In the IFT, we identified mycobacteria of the M. tuberculosis complex, the M. avium complex (M. avium, M. intracellulare and M. scrofulaceum) and M. kansasii with 10(7) bacteria. Using a panel of 105 mycobacterial patient isolates, we compared identification by WB and IFT with conventional, culture and biochemical identification. Identification of the M. tuberculosis complex in WB had a specificity and sensitivity of 96.3 and 98.3%, respectively. Identification in IFT of the M. tuberculosis complex had a specificity and sensitivity of 94.6% and 89.7%, respectively. Since the identification of mycobacteria with mAb requires only a small number of bacteria, these tests will reduce by several weeks the time necessary for microbiological identification.