Selective hydroxylation of benzene to phenol has been achieved using H2O2 in the presence Of a catalytic amount of the nickel complex [Ni-II(tepa)](2+) (2) (tepa = tris[2-(pyridin-2-yl)ethyl]amine) at 60 degrees C. The maximum yield of phenol was 21% based on benzene without the formation of quinone or diphenol. In an endurance test of the catalyst, complex 2 showed a turnover number (TON) of 749, which is the highest value reported to date for molecular catalysts in benzene hydroxylation with H2O2. When toluene was employed as a substrate instead of benzene, cresol was obtained as the major product with 90% selectivity. When (H2O2)-O-18 was utilized as the oxidant, O-18-labeled phenol was predominantly obtained. The reaction rate for fully deuterated benzene was nearly identical to that of benzene (kinetic isotope effect = 1.0). On the basis of these results, the reaction mechanism is discussed.