Abstract: The present invention is directed to novel methodology whereby different populations of the tuberculosis bacterial pathogen, Mycobacterium tuberculosis, or related Mycobacteria, can be genetically classified in relation to other isolates. Sites in the genome of Mycobacterium, which define previously unrecognized points of variability, are disclosed. The existence of this variability is of use to the clinician in order to consistently determine the identity of isolates of Mycobacterium responsible for individual cases of disease or disease outbreaks, thus suggesting appropriate choices for treatment protocols.