The present study is concerned with the numerical prediction of planar and axially-symmetric sudden expansion flows, using the Navier-Stokes as well as the boundary layer equations. The vorticity-steam function Navier-Stokes equations are solved by means of a robust multigrid block-line-Gauss-Seidel method. The corresponding boundary layer equations are solved at every longitudinal station by means of an incremental block-implicit scheme, using the Newton method combined with a deferred correction strategy to achieve fast convergence on the nonlinear terms. Accurate solutions to the Navier-Stokes equations and to the boundary layer equations with and without the FLARE approximation are provided for both planar and axially-symmetric expansions. © 1989.