A 63 year-old man with a history of anal carcinoma treated by surgery, chemotherapy and radiotherapy was admitted to our hospital two years later with small bowel obstruction requiring emergency surgery. Fifteen days later, he had to be operated on once again. During the procedure, severe metabolic alkalosis developed: pH 7.58, CO3H- 47.7 mmol/L and a base excess of 24.3 mmol/L. The patient had the following preoperative risk factors for hypochloremic metabolic alkalosis: low levels of Cl and K, prolonged aspiration of gastric contents, low plasma volume and parenteral nutrition. Metabolic alkalosis was managed with 250 mL of 7.5% hypertonic saline, 40 mEq of KCl, readjustment of the ventilatory pattern, perfusion of lactated Ringer's solution instead of 0.9% saline and administration of omeprazole. Response to treatment was good as elevated values fell to acceptable levels within two hours. Metabolic alkalosis is a common acid-base balance disorder which arises for a variety of reasons and which has significant anesthetic implications. Hypertonic saline may be useful for treating severe, acute hypochloremic metabolic alkalosis.