From January 1993 through February 1995, CDC and state health departments completed investigations of six instances in which passengers or flight crew traveled on commercial aircraft while infectious with tuberculosis (TB). All six of these investigations involved symptomatic TB patients with acid-fast bacillus (AFB) smear-positive cavitary pulmonary TB, who were highly infectious at the time of the flight(s). In two instances, Mycobacterium tuberculosis isolated from the index patients was resistant to both isoniazid and rifampin; organisms isolated from other cases were susceptible to all antituberculous medications. In addition, in two instances, the index patients were aware of their TB at the time of travel and were in transit to the United States to obtain medical care. However, in none of six instances were the airlines aware of the TB in these passengers. This report summarizes the investigations by CDC and state health departments and provides guidance about notification of passengers and flight crew if an exposure to TB occurs during travel on commercial aircraft.