High-frequency jet ventilation using a jet injector located at the right mainstem bronchus was superimposed on standard mechanical ventilation to ventilate the injured lung of a patient with unilateral massive atelectasis secondary to pulmonary hemorrhage. This technique of differential ventilation markedly improved arterial oxygenation in this patient and may prove to be a simpler modality of respiratory support in patients who have respiratory failure from unilateral lung disease.