Describe characteristics of preterm infants exposed to inhaled nitric oxide (iNO) in Kaiser Permanente Southern California. Case review of preterm infants <34-weeks exposed to iNO during 2010-2020 including respiratory and echocardiographic status, NICU course, and 12-month follow-up. 270 infants, 2.63% of births<34 weeks, (median, range: 26.1, 225/7-336/7 weeks gestation) were exposed to iNO. Median FiO2 at iNO initiation was 1.0 (IQR 0.94-1.0). Pulmonary hypertension (PH) was not associated with risk-adjusted 2 h oxygenation response or improved survival. Mortality to NICU discharge was 37.4%. Median cost of iNO was $7,695/patient. Discharged survivors experienced frequent rehospitalization (34.9%), use of supplemental oxygen, sildenafil, diuretics, bronchodilators, and steroids. Four infants had persistent PH. Five infants died after NICU discharge. Preterm infants receiving iNO have high mortality and 1st year morbidity. As currently used, iNO may be an indicator of respiratory diseaseseverity rather than mediator of improved outcomes.