This article analyzes the barotropic circulation in the Southwestern Atlantic Shelf using a three-dimensional numerical model forced with winds and tides. South of 40¿S, the shelf circulation is dominated by the propagation of the semidiurnal tides. In this region the diurnal tides are generally weak, except at the shelf edge where they resonate with northward propagating, continental shelf waves. North of 40¿S, the tidal circulation is relatively weak, and the circulation is mainly driven by the winds. The wind-driven annual mean circulation is characterized by a broad northeastward flow south of approximately 40¿S and is characterized by a southwestward flow farther north. The intense mixing associated with the Patagonian tides enhances the bottom friction that balances the energy input from the wind stress forcing. In contrast with previous results our simulation shows a detrainment of the northward volume transport with latitude due to an offshore flow along the edge of the Patagonian shelf break. The largest seasonal variations of the shelf circulation are observed in the region between 45¿S and 25¿S where, during the fall, there is a development of a clockwise gyre and a northeastward flow north of 40¿S. The gyre weakens toward the winter, and the northeastward flow reverses directions.