In absence of energy barrier, the long-range interactions between reactants should play an important role on the dynamics of the reaction of O (D-1) with H-2 that mainly occurs in the ground state potential energy surface for H2O. Quasiclassical and capture studies on a new potential energy surface that carefully reproduces these interactions are in close agreement with the most recent estimates for the thermal rate constant, when the effects of the excited surfaces are taken into account. (C) 2003 Published by Elsevier B.V.