Persistent elevation of pulmonary vascular resistance represents a major cause of death in infants with congenital diaphragmatic hernia.1 The present report describes an infant with diaphragmatic hernia in whom persistent pulmonary hypertension associated with severe hypoxemia was successfully treated with tolazoline hydrochloride. CASE REPORT A 3,250-g term boy was born at Boston Hospital for Women to a 31-year-old, gravida 2, para 1 woman. Pregnancy was unremarkable and labor lasted 12 hours. At delivery, Apgar scores were 5 at one minute and 7 at three minutes. There was extreme respiratory distress and hypoxemia. Intubation and a subsequent chest x-ray film led to the diagnosis of a diaphragmatic hernia.