OBJECTIVE Systemic vasodilatation in cirrhosis may lead to hemodynamic alterations with reduced effective blood volume and decreased arterial blood pressure. This study investigates the response of acute volume expansion on hemodynamics and regional blood volumes in patients with cirrhosis and in controls. METHODS Thirty-nine patients with cirrhosis (12 patients with Child-Turcotte class A, 14 with class B, and 13 with class C) and 6 controls were studied. During hepatic vein catheterization, cardiac output, systemic vascular resistance, central and arterial blood volume, noncentral blood volume, and arterial pressure were determined before and during a volume expansion induced by infusion of a hyperosmotic galactose solution. RESULTS During volume expansion, the central and arterial blood volume increased significantly in patients with class A and controls, whereas no significant change was found in patients with either class B or class C. Conversely, the noncentral blood volume increased in patients with class B and C. In both patients and controls, the cardiac output increased and the systemic vascular resistance decreased, whereas the mean arterial blood pressure did not change significantly. CONCLUSIONS Only in mild cirrhosis is the effective blood volume able to increase in response to volume expansion. Our results are consistent with the peripheral vasodilatation hypothesis and the circulatory hyporeactivity occurring in advanced cirrhosis.