Studies performed during the last decade have identified NAD(P)H oxidases unique to nonphagocytic vascular cells. The reactive oxygen species released from these enzymes regulate fundamental cellular functions such as growth (hyperplastic or hypertrophic), endothelial dysfunction, migration and inflammation, which have been demonstrated to play a role in atherogenesis. Evidence from experimental animal and human studies implicate the nonphagocytic NAD(P)H oxidases in multiple aspects of atherogenesis, suggesting that these enzymes may be important determinants of the course of vascular disease.