Ten patients clinically diagnosed as having perinatal aspiration syndromes were found to have pulmonary hypertension. These infants were either term or postmature babies and had the following characteristics: (1) systemic or suprasystemic levels of pulmonary artery pressure (range, 50 to 117 mm Hg); (2) a degree of pulmonary hypertension not related to the degree of aspiration evident on chest roentgenograms; (3) evidence of right-to-left shunting at the ductal or foramen ovale level; and (4) sustained severe hypoxemia despite 100% inspired oxygen concentration. The overall mortality for the group was 50%. Since these patients had marked clinical and physiologic similarities to patients previously reported as having the persistent fetal circulation syndrome (PFC), they were classified as having "PFC with aspiration." The existence of pulmonary hypertension should be suspected despite roentgenographic evidence of aspiration in any patient who also manifests the clinical characteristics of PFC because its treatment may alter the prognosis of such patients.