We present a realistic ab initio quantum scattering (AIQS) calculation for the chemical reaction H-2+OH --> H+H2O using the rotating bond approximation (RBA), based on a dual-level MP4//SAC (the fourth order Moller-Plesset perturbation theory/scaling all correlation) method with the 6-311+G(d,p) basis set. The MP4//SAC results give a vibrationally adiabatic ground state barrier height of 0.2722 eV. Calculated thermal rate constants are in good agreement with experimental measurements. (C) 2000 American Institute of Physics. [S0021-9606(00)31009-1].