We present six-dimensional (613) quantum dynamics calculations of initial state-selected reaction probabilities for the reaction of OH(upsilon = 0,j = 0) with CO(upsilon = 0,j = 0), for total angular momentum J = 0, The results are compared to five-dimensional (5D) calculations in which the potential was averaged over the vibrational ground state wavefunction of CO. The 6D reaction probabilities are in good overall agreement with the 5D results up to a collision energy E-i of 0.47 eV, but they exceed the 5D values at larger energies, by up to 40% at E-i = 0.8 eV. Significant vibrational excitation of the CO fragment occurs for E-i greater than or equal to 0.4 eV. (C) 2002 Elsevier Science B.V. All rights reserved.