Preface. 1. Introduction. 2. The chronology of mycobacteria and the development of mycobacterial ecology. 3. Classification of mycobacteria with regard to their ecology. 4. Environments providing favourable conditions for the multiplication and spread of mycobacteria. 5. Mycobacteria as habitat microorganisms of sphagnum bog vegetation. 6. Possible convergence towards pathogenicity in environmentally-derived mycobacteria. 8. Allergic reactions provoked by environmental mycobacteria. 9. Is the eradication of mycobacterioses possible? 11. The biological role of mycobacteria in the environment: Mycobacteria as nutrients in the development cycle of moorland dragonflies. 12. Expected future trends in mycobacteria and mycobacterioses. References.