Blood pressure (BP) increases after menopause. However, the mechanisms responsible have not been elucidated. In this study we tested the hypothesis that 20-hydroxyeicosatetraenoic acids (20-HETE), produced by cytochrome P-450 (CYP450) ω-hydroxylase, contributes to the hypertension in a model of postmenopausal hypertension, aged female spontaneously hypertensive rats (PMR). 1-Aminobenzotriazole, a nonselective inhibitor of arachidonic acid metabolism, for 7 days, reduced BP in PMR but had no effect in young females. Acute intravenous infusion of HET-0016, a specific inhibitor of 20-HETE, over 3 h, also reduced BP in PMR. CYP4A isoform mRNA expression showed no difference in renal CYP4A1 or CYP4A3 but increases in CYP4A2 and decreases in CYP4A8. CYP4A protein expression was decreased in kidney of PMR compared with young females. Endogenous 20-HETE was significantly higher in cerebral vessels of PMR than young females (YF) but was significantly lower in renal vessels of PMR. Omega-hydroxylase activity in cerebral vessels was also higher in PMR but was similar in kidney vessels in both groups. In renal microsomal preparations, endogenous 20-HETE was not different in PMR and young females, but ω-hydroxylase activity was significantly lower in PMR than YF. The data with blockers suggest that 20-HETE contributes to postmenopausal hypertension in SHR. The data also suggest that cerebral production of 20-HETE may be increased and renal tubular production may be decreased in PMR, thus both contributing to their elevated BP.