Intravenous hydralazine therapy in severe preeclampsia-eclampsia may be administered by either continuous intravenous infusion or intermittent bolus therapy. We studied the hemodynamic effects of continuous intravenous hydralazine infusion in seven patients with severe pregnancy-induced hypertension. The starting infusion dose was 5 mg/hr and was increased every 15 to 20 minutes by 1 to 2 mg/hr to obtain a 20% reduction in mean arterial blood pressure. The initial mean systolic and diastolic blood pressures were 208.3 +/- 24.8 and 124.3 +/- 11.6 mmHg, respectively. The comparable mean levels following hydralazine therapy was 144 +/- 13.6 and 87 +/- 11.6 mmHg. This decline was obtained at a mean hydralazine dose of 16.04 +/- 3.65 mg/hr. Despite an increase in cardiac output, the rapid uncontrolled decline in blood pressure resulted in five of the seven patients developing fetal distress requiring cesarean delivery. If hydralazine therapy is to be used in severe preeclampsia-eclampsia, we advocate avoidance of continuous intravenous therapy.