Acute pulmonary embolism increases pulmonary vascular resistance and may lead to acute right ventricular failure and cardiocirculatory collapse and respiratory failure, possibly resulting in substantial morbidity and mortality. Inhaled nitric oxide (NO) dilates pulmonary blood vessels and has been used to reduce pulmonary vascular resistance in patients with chronic thromboembolic pulmonary hypertension and acute respiratory distress syndrome. This case series describes our experience with inhaled NO administered to four patients suffering from acute massive pulmonary embolism following abdominal surgery. The four described patients recovering from small bowel resection, pancreatoduodenectomy, hemipelvectomy, or recent gastrointestinal bleeding had severe respiratory and hemodynamic deterioration due to pulmonary embolism. Each received inhaled NO (20-25 ppm) via the inspiratory side of the breathing circuit of the ventilator. Pulmonary and systemic blood pressures, heart rate, and lung gas exchange improved in all the patients within minutes after the initiation of NO administration. Inhaled NO may be useful in treating acute massive pulmonary embolism. This potential application warrants further investigation.