The following modifications to the polaro-graphic oxygen electrode method for SOD activity determination were made: (1) directly determining at room temperature, (2) introducing standard SOD as activity unit standard,(3) using phosphate buffer as reaction medium, and (4) increasing the pyrogallic acid used. These modifications result in: (1) the abolishment of the bubbles easily produced onthe electrode surface which severely interfere with the determination, (2) increased sensitivity of determination and (3) broadened linear range of SOD activity.