The effect of employing accurate transport properties in simulations of freely propagating H-2/O-2/He and CH4/O-2 flames is investigated. Transport properties for the collision pairs H-2-H-2, H-H-2, and H-H are computed from published tables of collision integrals. Previous calculations in our group of transport properties for OH-He, H-H2O and H-O-2 have been extended to higher temperatures. In addition, new calculations on H-He, O-He, H-2-He, and H2O-He are reported. Flame simulations with two sets of transport data were compared. The first set contained transport properties obtained with the conventional method of employing parameterized Lennard-Jones (12-6) potentials, while in the second set transport properties for the above collision pairs were substituted. A modest increase in laminar flame speeds, comparable to differences found when employing different chemistry models, was found for both flames. (C) 2015 The Combustion Institute. Published by Elsevier Inc. All rights reserved.