Three different discretization schemes were used to study the flow in a 90-degree bend square duct. The numerical method consists of a general curvilinear coordinate formulation of the governing equations and a non-staggered grid for the variables. A stable method of implementing the higher-order schemes is proposed. The second-order upwinding and QUICK schemes give results which compare more favourably with the experimental data than the first-order upwinding method. In 3-D flow problems, the grid-refinement is severely limited by the amount of computer storage and the use of higher-order upwinding schemes provides a better alternative in obtaining accurate flow predictions.