Bacteria have evolved a diverse potential to transform and even mineralize numerous organic compounds of both natural and xenobiotic origin. This article describes the occurrence of N-heteroaromatic compounds and presents a review of the bacterial degradation of pyridine and its derivatives, indole, isoquinoline. and quinoline and its derivatives. The bacterial metabolism of these compounds under different redox conditions - by aerobic, nitrate-reducing sulfate-reducing and methanogenic bacteria - is discussed. However, in natural habitats, various environmental factors. such as sorption phenomena, also influence bacterial conversion processes. Thus, both laboratory and field studies are necessary to aid our understanding of biodegradation in natural ecosystems and assist the development of strategies for bioremediation of polluted sites. Occurring predominantly near (former) wood-treatment facilities, creosote is a frequent contaminant of soil, subsoil, groundwater, and aquifer sediments. In situ as well as withdrawal-and-treatment techniques have been designed to remediate such sites, which are polluted with complex mixtures of aromatic and heterocyclic compounds.