Three patients with the obesity hypoventilation syndrome and one patient with the sleep apnea syndrome underwent gastroplasty for weight reduction. A tracheostomy was also performed in the patient with sleep apnea. The PaO2 rose from an average of 51 +/- 9 to 71 +/- 5 torr and the PaCO2 fell from an average of 51 +/- 21 to 41 +/- 6 torr within two to ten months following bariatric surgery. The improved arterial blood gases were associated with an increased forced vital capacity in each patient. The change in maximum voluntary ventilation was variable. Sleep capneography demonstrated cure of the patient with sleep apnea permitting removal of the tracheostomy. All four patients have returned to productive lives in society. Given proper pre- and postoperative care, patients with respiratory insufficiency tolerate the operation well. Respiratory insufficiency associated with morbid obesity should be considered an indication for the gastroplasty procedure, rather than a contraindication as previously suggested.