A kinetic theory collisional production model is used to determine the product velocity distributions of H and D resulting from collisional energy transfer with hot oxygen. The energetic oxygen atoms are the products of the dissociative recombination of O2+. Quantum mechanical cross sections for O-H and O-D collisions are used to determine the production distributions. The distributions of the particles entering a collision are assumed to be Maxwellian functions. The fraction of atoms with speeds above the escape speed is determined for Venus and Mars. For Venus, available density and temperature profiles are used to obtain estimates of the H and D escape fluxes and fractionation ratios. ¿ 1999 American Geophysical Union