Detailed information dealing with the ecology of mycobacteria is derived from a variety of different scientific fields such as botany, biochemistry, genetics, immunology, microbiology and epidemiology. This text attempts to evaluate this information from an ecological point of view and to develop a strategy for the prevention of tuberculosis and other mycobacterioses based on the ecological behaviour of mycobacteria, especially the potentially pathogenic species capable of either growth in the environment or provoking disease. Regarding the interests of the developing countries, special attention is paid to the ecology of Mycobacterium leprae and to the supporting effect of accompanying mycobacteria in its pathogenicity. On a more positive side, environmental mycobacteria play an important role in the ecology of moorland dragonflies.