Following the recognition of nitric oxide (NO) as the "endothelium-derived relaxing factor," an explosion of laboratory and clinical research led to the development of inhaled NO as a potential therapy for patients with pulmonary arterial hypertension (PAH). Despite clear demonstration of its selective and potent pulmonary vasodilator properties, inhaled NO therapy has only been formally approved by the US Food and Drug Administration and European Medicine Evaluation Agency for clinical use in the treatment of term and near-term infants with severe persistent pulmonary hypertension of the newborn (PPHN) with acute hypoxemic respiratory failure. Over the past decades, inhaled NO remains the central therapy for PPHN and is commonly used for acute pulmonary vasoreactivity testing during right heart catheterization and for treating pediatric and adult patients with PAH associated with postoperative cardiac surgery, severe respiratory failure, pulmonary hypertension crises, and other disorders. This review will describe the current use of inhaled NO in clinical practice and briefly discuss its potential role for the treatment of chronic PAH.