Quantum scattering calculations are reported for the O(P-3)+H-2(v=0,1) reaction using chemically accurate potential energy surfaces of (3)A' and (3)A" symmetry. We present state-to-state reaction cross sections and rate coefficients as well as thermal rate coefficients for the title reaction using accurate quantum calculations. Our calculations yield reaction cross sections that are in quantitative accord with results of recent crossed molecular beam experiments. Comparisons with results obtained using the J-shifting calculations show that the J-shifting approximation is quite reliable for this system. Thermal rate coefficients from the exact calculations and the J-shifting approximation agree remarkably well with experimental results. Our calculations also reproduce the markedly different OH(v'=0)/OH(v'=1) branching in O(P-3)+H-2(v=1) reaction, observed in experiments that use different O(P-3) atom sources. In particular, we show that the branching ratio is a strong function of the kinetic energy of the O(P-3) atom. (C) 2004 American Institute of Physics.