The isotopic branching on the reaction of O(D-1) + HD has been the subject of several theoretical and experimental studies with results ranging from 1 to 2 for the OD/OH product ratio. We present a study of the dynamics of this reaction using a double-valued potential energy surface for the ground state water molecule. Our results predict a branching ratio close to 2 for this reaction in agreement with statistical studies but in contrast with experiment. This result can be attributed to the formation and dynamics of the intermediate complex. (c) 2006 Elsevier B.V. All rights reserved.