Given the large number of treatments used in neonates with PPHN, we wished to document treatment of PPHN and outcomes of those treatments. Therefore, we performed a prospective, observational study to document prevalence of PPHN, the treatments and outcomes in a large population of infants treated at the 12 centers of the National Institute of Child Health and Human Development (NICHD) Neonatal Research Network. Further, we sought to compare treatment with hyperventilation to treatment with alkali infusion.