Patients who manifest free anxiety excrete excessive amounts of hippuric acid. Successful treatment reduces the anxiety and hippuric acid excretion to normal level. The hippuric acid excretion in the anxiety group is significantly greater than in a control group. Catatonic schizophrenics excrete less hippuric acid than the healthy control. Successfully treated, the level of hippuric acid secretion is raised to normal. The differences noted are statistically significant. Mild external (real) stress does not produce abnormal excretion. The relation of these findings to the general theory of anxiety is elaborated.