Nitric oxide production appears to be decreased in infants with persistent pulmonary hypertension (PPHN). Inhaled nitric oxide may improve oxygenation by two mechanisms: increased pulmonary blood flow and improved ventilation-perfusion matching. Nitric oxide inhalation has been tested in newborns with PPHN, congenital heart diseases, and bronchopulmonary dysplasia. We present a review of the articles concerning inhaled nitric oxide for infants with PPHN. Overall, 59% of the neonates had an initial improvement in oxygenation in response to nitric oxide inhalation. A sustained response was observed in 60% of the infants. Patients with extrapulmonary shunting, clear chest radiographs, and adequate lung volume seem to have a better response, whereas patients with congenital diaphragmatic hernia, severe sepsis, and alveolar capillary dysplasia are more likely to fail. To define the benefit-risk ratio, six prospective randomized trials are currently in progress.