Large Eddy simulations (LES) of compressible mixing layers are carried out to investigate scalar mixing. Convective Mach numbers of the simulations range from M-c = 0. 16 to M-c = 1.1. In this study, the ability of two subgrid models (the dynamic Smagorinsky model and the dynamic mixed model) to predict scalar mixing in compressible shear layers is assessed. Comparisons of the results with experimental data show that the two subgrid closures are capable of capturing the principal effects of compressibility on scalar mixing, especially the decrease of scalar statistics and the changes in the shape of turbulent structures. (c) 2007 Elsevier Ltd. All rights reserved.