Four strains of Pseudomonas putida (NAH), Pseudomonas sp.(TOL), Achromobacter xylosoxidans, and Alcaligenes sp. were compared with their degradative capability of aromatic compounds. All of the bacterial strains were utilized catechol as a sole carbon source for growth, but signigicantly different in degradative properties for 5 other aromatic compounds. Catechol 2, 3-dioxygenase gene from P. putida (NAH) has been cloned and expressed in E. coli. The DNA clone designated pCNU101 contains NAH-derived 6 Kb insert and its physical map was characterized. A subclone (pCNU106) for the catechol dioxygenase gene in pCNU101 contained 2.0kb-DNA insery fragmented by HpaI and ClaI.