During June-August 1998, the Tuberculosis (TB) Control Program of the Baltimore City Health Department (BCHD) identified four cases of TB among young black men. Three of these men also had human immunodeficiency virus (HIV) infection. The four reported belonging to a social network of transgender persons (i.e., persons who identify with or express a gender and/or sex different from their biologic sex) (1). By October 1998, test results on Mycobacterium tuberculosis isolates from the four men demonstrated a matching 11-band DNA fingerprint pattern (2), suggesting that these case-patients were epidemiologically linked. This report describes the public health investigation of these TB case-patients to identify contacts in Baltimore and the New York City area (NYC); the findings suggest that an interstate outbreak of TB has occurred within a social network that includes transgender persons.