The quantitative impact of mesenteric vasoconstriction on the systemic hemodynamic response to cardiogenic shock induced by pericardial tamponade was evaluated. Graded increases in pericardial pressure produced corresponding decreases in cardiac output to 44% ± 2% and arterial pressure to 64% ± 3% of baseline and increases in total peripheral vascular resistance to 131% ± 4% of baseline. Total mesenteric blood flow decreased disproportionately, to 28% ± 3% of baseline, because of a disproportionate increase in mesenteric vascular resistance to 223% ± 6% of baseline. Nonmesenteric vascular resistance increased only to 119% ± 4% of baseline. Thus mesenteric vasoconstriction accounted for 42% of the increase in total peripheral resistance. Prior blockade of the renin-angiotensin axis ablated this response and eliminated the mesenteric contribution to systemic vascular resistance, while confirmed blockade of the α-adrenergic system or vasopressin system had no effect. Without shock, central intravenous infusions of angiotensin II (but not norepinephrine or vasopressin) closely mimicked this selective vasoconstriction. Angiotensin-mediated selective mesenteric vasoconstriction accounts for more than 40% of the overall increase in systemic vascular resistance in cardiogenic shock. © 1992.