Members of the superfamily of cysteinate-heme enzymes are referred to as Cytochrome P450 (CYP) and are key mediators of the oxidative transformation of exogenous molecules. They are classified into families, subfamilies, and individual isoenzymes based on similarities in their amino acid sequence. Many CYP enzymes are not only involved in the metabolism of xenobiotics, but also a host of endobiotics whose metabolites are biologically active and play critical roles in the maintenance of essential body functions. Recently, some CYP enzyme families have been identified in the heart, endothelium and the smooth muscle of blood vessels. Since endogenous CYP-derived substances such as epoxyeicosatrienoic acids (EETs), hydroxy-eicosatetraenoic acids (HETEs), prostacyclin (PGI₂), aldosterone, and sex hormones served as physiological factors in the regulation of renal function and vascular tone, CYPs themselves are very interesting as enzymes that may be involved in the pathogenesis of cardiovascular disease. Polymorphisms in the coding or promoter regions of the CYP genes can affect the function of the CYP enzymes. Identification of polymorphisms and the associated phenotypes will almost certainly help to elucidate the role of CYPs and their products in the modulation of cardiovascular function. Recently some genetic variants in the CYP genes have been reported to be associated with hypertension. The focus of this review is to summarize the CYP genes involved in essential hypertension.