Despite the high incidence of sudden death in pregnant patients with primary pulmonary hypertension (PPH) and heart failure, no data are available that thoroughly elucidate the peripartum hemodynamic alterations occurring in these patients. The present report describes the clinical course of a pregnant patient with PPH and provides data regarding peripartum hemodynamic alterations. Hemodynamic parameters were stable during labor and delivery, but pulmonary vascular resistance rose gradually while cardiac output fell after parturition. Dobutamine caused a modest but unsustained increase in cardiac output. Nitroprusside produced a significant sustained augmentation of cardiac output from 3.5 to 5.0 liters/min due to reduction of systemic and pulmonary vascular resistances, and permitted restoration of hemodynamic stability and resolution of heart failure. The authors believe that pregnant patients with PPH and severe heart failure in whom abortion is not possible should have complete hemodynamic monitoring during parturition and for several days thereafter. Segmental epidural anesthesia and lateral positioning of the patient minimize hemodynamic alterations during labor and delivery. Nitroprusside and dobutamine may be effective for treatment of congestive heart failure.