A selective review of several bacterial forms of cytochrome P450 enzymes is reported. The importance of such enzymes for biotechnology is emphasized. together with various relevant aspects of the P450 system, in the light of recent developments from molecular biology and X-ray crystallographic structure determination. The role of molecular modelling and quantitative structure-activity relationships (QSARs) for the development of new chemical entities (NCEs) is discussed, together with the relevance of functional genomics to the biotechnological exploitation of certain bacterial strains. (C) 2004 Elsevier Inc. All rights reserved.