Several lines of evidence indicate a significant association between variations of the endothelial constitutive nitric oxide synthase gene and the incidence of cardiovascular disease, and discrepant findings may be attributable to racial differences. The detection of functional allelic polymorphisms may be needed to confirm this association, because direct evidence to support a causative role for the endothelial constitutive nitric oxide synthase gene is not yet available. There are no available data to confirm that neural and inducible nitric oxide synthases are associated with cardiovascular diseases.