To identify the E-prostanoid (EP) receptors that mediate the hemodynamic actions of PGE₂, we studied acute vascular responses to infusions of PGE₂using lines of mice in which each of four EP receptors (EP₁ through EP₄) have been disrupted by gene targeting. In mixed groups of males and females, vasodepressor responses after infusions of PGE₂were significantly diminished in the EP₂ −/− and EP₄ −/− lines but not in the EP₁ −/− or EP₃ −/− lines. Because the actions of other hormonal systems that regulate blood pressure differ between sexes, we compared the roles of individual EP receptors in males and females. We found that the relative contribution of each EP-receptor subclass was strikingly different in males from that in females. In females, the EP₂ and EP₄ receptors, which signal by stimulating adenylate cyclase, mediate the major portion of the vasodepressor response to PGE₂. In males, the EP₂ receptor has a modest effect, but most of the vasodepressor effect is mediated by the phospholipase C-coupled EP₁receptor. Finally, in male mice, the EP₃ receptor actively opposes the vasodepressor actions of PGE₂. Thus the hemodynamic actions of PGE₂ are mediated through complex interactions of several EP-receptor subtypes, and the role of individual EP receptors differs dramatically in males from that in females. These differences may contribute to sexual dimorphism of blood pressure regulation.