OBJECTIVE: To test the hemodynamic efficacy and feasibility of nitric oxide (NO) administration by oxygen hood in neonatal pulmonary hypertension. STUDY DESIGN: A double-hood apparatus was used in which a combination of NO, O(2), and N(2) was introduced into the inner hood and suctioned from the outer hood. Chronically instrumented non-intubated piglets were exposed to 10% O(2) (hypoxia; n=8) or group B streptococci infusion (GBS; n=5) to produce pulmonary hypertension and were then exposed to 20 ppm NO. RESULTS: NO decreased (>50%) pulmonary artery pressure and vascular resistance in both hypoxia- and GBS-induced pulmonary hypertension, with minimal effects on systemic arterial pressure and cardiac output. NO administration could be performed without detectable environmental leakage. CONCLUSION: Hood NO administration is feasible and shows hemodynamic efficacy in neonatal piglets with pulmonary hypertension.