We investigated a cluster of patients with tuberculosis (TB) in North Carolina and determined the extent of transmission of 1 strain of Mycobacterium tuberculosis. A retrospective cohort study was conducted. Homeless shelter attendance and medical records for 1999 and 2000 were reviewed. The period of exposure to M. tuberculosis was determined, and shelter residents were offered TB screening. DNA fingerprinting was performed on 72 M. tuberculosis isolates. In addition to the initial index cluster of 9 patients, another 16 patients were identified. Isolates of M. tuberculosis from all 25 patients shared a matching DNA fingerprint pattern. All but 1 patient was male, 22 (88%) were African American, and 14 (56%) were human immunodeficiency virus-infected. An epidemiological link to a single shelter was identified for all but 1 patient. Earlier recognition of this shelter as a site of M. tuberculosis transmission could have been facilitated through innovative approaches to contact investigation and through genetic typing of isolates.