5, 10, 15, 20-tetraphenylporphyrinatocobalt(II) complex has been found to be an efficient catalyst for the oxidationn of 3,5-di-tert-butylcatechol to 3,5-di-tert-butylbenzoquinone by molecular oxygen) in dimethylformamide. Measurement of dioxygen uptake was used to monitor the oxidation process. The oxidation reaction rate constant was reported to be linearly related to the concentration of catalyst, and saturation kinetics were shown to be dependent on both 3,5-di-tert-butylcatechol concentration and dioxygen pressure. The Michaelis-Menten method was used to obtain the kinetic parameters. A mechanism also has been proposed according to kinetic data, production of a ternary complex involving catalyst, substrate, and dioxygen and the formation of the semiquinone anion radical (3,5-DBSQ.) which detected by ESR spectroscopy. The system investigated is a functional model of catecholase like activity, based on free-radical intermediates, a possibility recently demonstrated for certain oxidoreductases.