Based on field observations as well as results of hydrodynamic and sediment transport models, the relation between the asymmetry of the horizontal tide and that of the vertical tide and the relation between the asymmetry of the horizontal tide and the residual sediment transport in the Westerschelde have been analysed. This analysis has the objective to identify the significance of the tidal asymmetry for the morphological development in the estuary.For the local residual sediment transport, the residual current, i.e. the M0 component of the flow velocity, is the dominating factor of the asymmetry of the horizontal tide. The residual current is determined by the bathymetric characteristics and the phase difference between the horizontal tide and the vertical tide, rather than the overtides. For the integrated residual sediment transport through the estuary, both the residual current and the overtides are important. Further it is concluded that for residual sediment transport the sixth-diurnal tide is as important as the quarter-diurnal tide.