Although sensitive calorimetric procedures exist for the determination of aminophenols and aminobenzoic acids, their direct application to biological materials, e.g. urine is beset with difficulties and most usually wllen concentrations are low. Preliminary extraction appears to be a necessity, not only as an aid to concentration but to eliminate intcrfcring substances, e.g. phenols, hydroxy-aromatic acids. The use of solvent extraction and ion-exchange resins have been studied for this purpose. In this communication, investigations have been limited to o-and fi-aminophenols, o-and .$-arninobenzoic acids and 3-hydroxyanthranilic acid. Examples of typical results are shown. Anatysis of cxfracf EXPERIMENTAL -rhc following calorimetric methods wcrc employed to assess the quantity of substance under investigation in the various extracts. o-and $-aminobenzoic acids, diazotisation with nitrous acid followed by coupling with N-( I -naphthyl)-ethylcncdiaminc clihydrochloridc1.s. fi-Aminophcnol, indophcnol pigment formation in the prcscncc of o-crcsol and ammonias.4 or molyhdcnum blue formation5. 3-Hyclroxyanthranilic acid, indophenol pigment formation in the prcscncc of z,G-dichloroquinonc chlorimide4 or molybdenum blue formation*. o-aminophenol, indophcnol pigment formation in the prcscnce of, z,G-dichloroquinonc chlor-imid& or molybclcnum blue formations.