82 patients who had not specific disturbed conditions, were examined potassium metabolism with various surgical stress in pre-and post-anesthesia. Author determines degrees of surgical stress by factors of surgical duration and estimated blood loss. And measured potassium concentration, pH, pCO2, pO2 and osomlarity in serum on pre-and post-anestbetic pericd, with excreted urinary potassium during surgery. The results are followed; 1) The plasma potassium concentration was more decreased following severer surgical stress. 2) Uninary potassium concentration and amount were more increased following severer surgical stress. 3) The pathophysiology of potassium disturbance with surgical stress was asociated by increased secretion of mineralocorticoid and anti-diuretic hormone. 4) After post-anesthesia, patients with severe surgical stress should be measured serum potassium concentration and corrected.