The Navier-Stokes Equations.- Eddy Viscosity Models.- to Eddy Viscosity Models.- Improved Eddy Viscosity Models.- Uncertainties in Eddy Viscosity Models and Improved Estimates of Turbulent Flow Functionals.- Advanced Models.- Basic Criteria for Subfilter-scale Modeling.- Closure Based on Wavenumber Asymptotics.- Scale Similarity Models.- Boundary Conditions.- Filtering on Bounded Domains.- Near Wall Models in LES.- Numerical Tests.- Variational Approximation of LES Models.- Test Problems for LES.