In Quick's hippuric acid test, the benzoic acid administered as sodium benzoate brings two mechanisms into action in the liver: (1) the production of aminoacetic acid and (2) the conjugation of aminoacetic acid with benzoic acid to form hippuric acid. Quick1 stated that the diminution of hippuric acid formation in patients is due mainly to the reduced ability of the liver to synthesize aminoacetic acid and in part to damage of the enzymatic mechanism performing the conjugation. This suggests that patients with diminished hepatic ability to furnish aminoacetic acid should respond with an increase in excretion of hippuric acid if aminoacetic acid is administered along with sodium benzoate. On the other hand, patients in whom the conjugation process also is impaired should not show such an increase. METHOD To probe the validity of this assumption, we decided to determine the hippuric acid formation in patients to whom sodium benzoate