A simple amperometric method has been developed for the determination of amino groups on a solid support. The method is based on oxygen consumption during the reaction between the bifunctional reagent gluaraldehyde and the amino groups on the solid support. Oxygen consumption was monitored with a Clark oxygen electrode. AHSepharose 4B, Affi-Gel 102, and Amino-Celluofine were used as amino-terminal solid supports. The concentration of amino groups on each support was calculated from a calibration curve of the standard compound. When hexamethylenediamine was used as the standard, the concentration of amino groups on AH-Sepharose 4B and Affi-Gel 102 by the present method showed good agreement with that by the conventional method. In the case of Amino-Cellulofine, ethanolamine had to be selected as the standard. The relative standard deviation for six successive determinations of AH-Sepharose 4B was 3.2%; the polymerization of glutaraldehyde showed no effect on the result. The spectral property of AH-Sepharose 4B treated with glutataraldehyde showed no effect on the result. The spectral property of AH-Sepharose 4B treated with lutaraldehyde suggested that the reaction mechanism of the present method was based on the oxygen consumption during the formation of the pyridinium salt on the support. A comparative study of the present method with a colorimetric method with Traut's regent is also included.