Persons infected by Mycobacterium intracellulare, as demonstrated by positive skin test to the antigen, are concentrated in the southeastern coastal area of the United States. This geographical distribution is unlike that of persons exposed to M. tuberculosis and provides a hypothesis to the possible source of infection with M. intracellulare and other atypical Mycobacteria. Our research proposed to continue testing the hypothesis that the source of the infection is Mycobacteria residing in either the estuaries or fresh water of the southeastern United States or animals (birds especially) that are associated with these habitats. These Mycobacteria are concentrated at the surface of bubbles formed during wave action and rain or spread in dusts. The experimental approach involves sampling air as well as surface and subsurface waters and soils in various areas of the southeastern United States, at and off the coast of Virginia, South Carolina, Maryland, etc. Initial studies by the principal investigators have already demonstrated the effectiveness of this approach. The concentration of Mycobacteria, their frequency of isolation, and identification of each isolate will be part of this study. The data concentration and frequency of isolation, and identification of each isolate will be part of this study. The data of concentration and frequency of isolation will be compared to samples from areas where the incidence of infection with M. intracellulare is lower (upstate New York and New England). In addition, the physiological ecology of these organisms is being investigated to determine the basis for the unique geographical distribution.