Quantum chemical reactions, where the reaction coordinate is coupled to a bath or environment comprising other degrees of freedom of the system, are investigated. We approximate the quantum time evolution by quantum-classical Liouville surface-hopping dynamics. Within this framework, we explore the effect on the reaction rate of sampling the reaction coordinate and bath initial conditions from quantum and classical distributions. We find that the rate constant determined from quantum bath sampling is lower than that obtained from classical bath sampling. This is also shown to be the case for a simple analytically solvable two-dimensional reaction model. (c) 2006 Elsevier B.V. All rights reserved.