N-heterocyclic aromatic compounds are common contaminants associated with the use of hydrocarbons in both coal gasification and wood treatment processes. Those compounds have been found in groundwater, and many are known mutagens. It is obvious that in many cases the removal of those toxic compounds from our environment is a very complicated and expensive process. A method looking very promising is the one which employs the strains of chosen microorganisms and their biochemical pathways for biodegradation of a number of very dangerous compound like pyridine, quinoline, carbazole and derivatives of these compounds. Pyridine could be degraded through the same pathway under both aerobic and anaerobic conditions. The first step in this process is hydration. The mechanism of pyridine degradation involves N-C-2 (Nocardia Z1) or C-2-C-3 (Bacillus 4) ring cleavage. The metabolism of pyridine derivatives and other N-heterocyclic compounds like quinoline, carbazole or indole seems to be initiated by hydroxylation. The initial step in the transformation and a ring cleavage of quinoline derivatives can occur on either the heterocyclic or the homocyclic ring. In this article we reviewed the current status of this very difficult topic related to microbial degradation of N-heterocyclic compound.