A theory for chemical reaction dynamics in condensed phase systems based on the generalized Langevin formalism of Grote and Hynes [J. Chem. Phys. 73, 2715 (1980)] is presented. A microscopic approach to calculate the dynamic friction is developed within the framework of a combination of kinetic and mode-coupling theories. The approach provides a powerful analytic tool to study chemical reactions in realistic condensed phase environments. The accuracy of the approach is tested for a model isomerization reaction in a Lennard-Jones fluid. Good agreement is obtained for the transmission coefficient at different solvent densities, in comparison with numerical simulations based on the reactive-flux approach. (C) 2004 American Institute of Physics.