It was confirmed by using warburg respiro-meter that gallic acid and tannic acid whichhave been used as reagents of Bavendamm'sreaction were oxidized by both lactase and tyrosinase, whereas a-naphthol was oxidized byonly laccase, and tyrosine and p-cresol wereoxidized by only tyrosinase. Accordingly, it is to be desired that Baven-datum's reaction is divided into both laccaseand tyrosinase reaction by using a-naphtholand tyrosine or p-cresol respectively. According to the testing method of unit ofpenicillin activity (cup method) cylinders ofstainless steel were placed on the nutrient agarcontainin respective substrates, then laccaseand tyrosinase solution were pipetted into thecylinders. After 24 hrs, it was found thatoxidized colored zone with was similar to thatin Bavendamm's reaction in around thecylinders occured.