Although nontuberculous mycobacteria (NTM) infections are not common, there is evidence that they are becoming increasingly recognized and in some parts of the country occur more frequently than M. tuberculosis. The classic description of NTM pulmonary infection is that of a male patient with cavitary infiltrates and predisposing lung disease. With an increase in the number of reported cases of infection, there have been other syndromes described, particularly in elderly female patients without any predisposing conditions, those with asymptomatic pulmonary nodules, esophageal disease causing recurrent aspiration pneumonitis, and disseminated infection in AIDS. Therapy of M. avium complex (MAC) disease is far from definitive whereas infections due to M. kansasii can be effectively treated even in the presence of profound immunosuppression. Recognition of these infections and their recent change in epidemiology hopefully will encourage practitioners to enroll their patients into clinical protocols that will help to establish the optimal regimen(s).