The clinical characteristics and scores on the Minnesota Multiphasic Personality Inventory (MMPI) of 192 patients undergoing a five-hour oral glucose tolerance test (OGTT) for evaluation of reactive hypoglycemia were assessed. There were twice as many women as men. One hundred twenty-nine patients had spells of light-headedness, shakiness, diaphoresis, weakness, and fatigue. Hypoglycemic symptoms occurring during the test were not related to level of plasma glucose nadir or to rate of descent of glucose level. Hypoglycemia was not found when glucose levels were measured during occurrence of spontaneous symptoms in 86 patients. MMPI scores were significantly different from those of general medical patients. Both men and women evinced a conversion V profile. The five-hour OGTT seems unreliable for the diagnosis of reactive hypoglycemia, and most patients with symptoms suggestive of hypoglycemia may have emotional disturbances.