We evaluated prospectively the extent of trophoblastic embolization and its central hemodynamic effects during and after evacuation of large molar pregnancies in six women. A pulmonary artery catheter was inserted to obtain hemodynamic measurements as well as to obtain blood samples to identify trophoblasts before, during, and six hours after evacuation. Small numbers of both multinucleated giant cells and of large mononuclear cells with abundant cytoplasm were identified in the buffy coat of blood, aspirated in two cases before evacuation and for all six cases, during evacuation. There were no significant changes in heart rate or mean systemic arterial, pulmonary arterial, central venous, and pulmonary capillary wedge pressures; or cardiac output, stroke volume, and pulmonary or systemic vascular resistance when preevacuation preanesthetic values were compared with those six hours after evacuation. However, significant decreases in heart rate, mean arterial pressure, and pulmonary vascular resistance were observed during evacuation, which returned to preevacuation levels by completion of anesthesia.