We examined the hemodynamic and hemorheological effects of intravenous volume expansion in women with pre-eclampsia. 20 untreated women with moderate pre-eclampsia were randomized to receive a 500 ml infusion over 4 h of either hydroxyethylstarch (HAES steril 10%, HES) or NaCl 0.9% solution. After completion of the infusion trial all patients received oral antihypertensive drugs, bed rest and free sodium and water intake. The hemodynamic responses were measured by impedance cardiography. Hemorheological parameters and blood pressure were measured before and after (24 h later) infusion. The HES infusion but not NaCl leads to a significant reduction of hematocrit and erythrocyte aggregation. In addition to that there was a nonsignificant increase of the cardiac index in the HES-group but no changes in the heart rate. Intravenous volume expansion in women with pre-eclampsia with a long acting colloid like hydroxyethylstarch is associated with a significant influence on the flow properties (hematocrit and erythrocyte aggregation) of blood.