A 46-year-old woman was admitted to the metabolic ward of New England Medical Center Hospital (NEMCH) for evaluation of hypokalemia and metabolic alkalosis. The patient was in good health until four months earlier, when preoperative determination of serum electrolytes disclosed a serum potassium concentration of 3.0 mEq/liter and a bicarbonate concentration of 31 mEq/liter. A hysterectomy was performed without complications, and on discharge 80 mEq of potassium chloride per day was prescribed. One month later she was admitted to another hospital because of supraventncular tachycardia; hypokalemia had persisted. Evaluation revealed no evidence of organic heart disease and the arrhythmia was presumed to be secondary to hypokalemia. Two weeks later, she was readmitted for further evaluation. Blood pressure was 120/80 mm Hg; cardiac examination revealed normal S1 and S2 sounds and a grade 1/VI systolic ejection murmur at the lower left sternal border; abdominal examination revealed no abdominal masses; no edema was present. The remainder of the physical examination was normal. Laboratory findings revealed: serum creatinine, 0.7 mg/dl; BUN, 15 mg/dl; serum sodium, 138 mEq/liter; serum potassium, 2.9 mEq/liter; chloride, 96 mEq/liter; and bicarbonate, 34 mEq/liter; hemogram, serum calcium, serum phosphorus, serum albumin, serum