SUMMARYThe Multiple Semi-coarsened Grid (MSG) multigrid method of Mulder (J. Comput. Phys. 1989; 83:303 -323) is developed as a solver for fully implicit discretizations of the time-dependent incompressible Navier-Stokes equations. The method is combined with the Symmetric Coupled Gauss-Seidel (SCGS) smoother of Vanka (Comput. Methods Appl. Mech. Eng. 1986; 55:321-338) and its robustness demonstrated by performing a number of large-eddy simulations, including bypass transition on a at plate and the turbulent thermally-driven cavity ow. The method is consistently able to reduce the non-linear residual by 5 orders of magnitude in 40-80 work units for problems with signiÿcant and varying coe cient anisotropy. Some discussion of the parallel implementation of the method is also included.