An ongoing program is described which addresses the large-eddy simulation of non-premixed, turbulent reacting flows. Some background will be given on large-eddy simulation, mixture-fraction based models, and proposed subgrid-scale models, along with early results on a priori testing of these models. Recent evaluation of the models has involved the use of results of the direct numerical simulation of the homogeneous, isotropic decay experiments of Comte-Bellot and Corrsin (1971, J. Fluid Mech.). In addition to the velocity field, the simulations include the calculation of the mixture fraction and concentration fields for chemically-reacting species. Then further a priori and a posteriori testing of the subgrid-scale models is presented, in particular for the models for the filtered variance of the mixture fraction and its filtered dissipation rate, and the implications of these results on the modeling of filtered chemical reactions is discussed.