Swan-Ganz hemodynamic monitoring in 49 antepartum patients with severe preeclampsia revealed a variable hemodynamic profile. The majority of patients had normal left ventricular filling pressure (8.4 +/- 0.2 mm Hg), normal to high cardiac index (4.4 +/- 0.1 L.min-1.m2), and upper normal to moderately elevated systemic vascular resistance (1226 +/- 37 dynes.sec.cm-5). Eight patients had pulmonary edema and their findings included high wedge pressure (18 +/- 1 mm Hg), upper normal to high cardiac index (4.9 +/- 0.5 L.min-1.m2), and normal systemic vascular resistance (964 +/- 50 dynes.sec.cm-5). Left ventricular function was hyperdynamic in 73% of the 49 patients. Patients with chronic hypertension and superimposed preeclampsia were hemodynamically indistinguishable from patients with preeclampsia alone. We conclude that, in general, preeclampsia is a high cardiac output state associated with an inappropriately high peripheral resistance. The normal wedge and central venous pressures suggest central redistribution of intravascular volume if the generally accepted reports of decreased plasma volume in preeclampsia are correct.