The direct conversion of benzene to phenol by hydroxylation with hydrogen peroxide was carried out over various transition metals impregnated on MCM-41 and activated carbon. Copper-, iron-, and vanadium-impregnated on activated carbon gave better yields of phenol when compared to the corresponding reactions using cobalt-, nickel-, manganese-, and titanium-impregnated catalysts. Comparison of the MCM-41- and activated carbon-supported catalysts showed that activated carbon-supported catalysts gave a higher yield of phenol than did the MCM-41-supported catalysts. The activity of the transition metals supported on activated carbon in the production of phenol was V > Fe > Cu; the corresponding activity of the transition metals supported on MCM-41 was Cu > Fe > V. In addition to the role of transition metals in catalyzing the hydroxylation reaction, the hydrophobic nature of the activated carbon surface seems to enhance the performance of these catalysts relative to the MCM-4 1 -supported catalysts.