We describe a 40-yr-old woman who received inhaled nitric oxide (NO) as a therapeutic bridge to heart-lung transplantation for end-stage primary pulmonary hypertension. After 10 yr of increasing disability, the patient presented in October 1993 with severe dyspnea, right ventricular angina, and syncope. As predicted by a prior vasodilator trial, prostacyclin produced as initial favorable clinical and hemodynamic response. With the recurrence of severe symptoms and hemodynamic compromise, inhaled NO was successfully tried at 40 ppm, initially via a face mask and later via a transtracheal Scoop catheter. The patient was "bridged" to heart-lung transplant after 68 d of therapy (mean dose of NO, 50.4 +/- 23 ppm). The explanted lungs revealed no evidence of significant NO toxicity, and the explanted heart was successfully transplanted into another patient. Inhalation of NO via a transtracheal catheter is a useful and practical treatment of refractory pulmonary hypertension. The limits of NO therapy in terms of duration and dosage have not been determined.