Cytochrome P450 4F2 (CYP4F2) catalyzes the omega-hydroxylation of arachidonic acid to 20-hydroxyeicosatetraenoic acid (20-HETE), a natriuretic and vasoactive eicosanoid that participates in the development of hypertension. The relationship among CYP4F2 genetic variants in the regulatory region, formation of renal 20-HETE, and hypertension is unknown. Here are reported seven genetic variants around the CYP4F2 intronic regulatory region. Four of these variants made up two common haplotypes, Hap I (c.-91T/c.-48G/c.-13T/c.+34T) and Hap II (c.-91C/c.-48C/c.-13C/c.+34G). Hap I included a major functional variant, c.-91T-->C, which was identified by reporter assay and electrophoretic mobility shift assay. Transfected into HEK293 cells, the Hap I construct showed a trend toward higher basal transcriptional activity and exhibited significantly greater LPS-stimulated activity than Hap II; these findings were the result of different NF-kappaB binding affinity between the two constructs. In vivo, a case-control study demonstrated that homozygosity for Hap I doubled the risk for hypertension in a Chinese population, even after adjustment for risk factors including age, gender, and body mass index. This association was confirmed in a family-based association study. In addition, Hap I was associated with elevated urinary 20-HETE. These results indicate that a functional variant of the CYP4F2 regulatory region, which increases the binding affinity of NF-kappaB, increases the risk for hypertension, likely by modulating the production of 20-HETE.