We describe eight patients who had terminal lung cancer causing severe dyspnea unrelieved by oxygen, nonnarcotic drugs, or intermittent bolus narcotics. We treated these patients with continuous intravenous infusion of morphine, beginning with bolus IV injections of 1 or 2 mg of morphine every 5 to 10 minutes until the patient reported relief. A continuous morphine infusion was then started, with the hourly dose equal to 50% of the cumulative bolus dose. Vital signs, degree of sedation, and blood gases were serially followed. Six patients achieved good dyspnea relief, one had moderate relief, and one had a poor response. Variable changes were noted in the PaO2, whereas PaCO2 steadily increased in five of seven patients, and pH decreased in six. There was little change in systolic blood pressure or pulse, and only one individual had less than 10 respirations per minute. The major side effect of treatment was sedation, treated by temporarily discontinuing morphine until the patients' mental status improved and then restarting the infusion at a 50% lower hourly morphine dose. Mean time of study was 30 hours (range 16 to 87 hours). Seven of the eight study patients died during treatment. Whether morphine therapy shortened survival is uncertain. We conclude that continuous morphine infusion is effective therapy for severe dyspnea. The treatment is ethically justified. Relief of suffering is the primary goal of therapy, and less risky treatments are unavailable.