We use hydrographic data to delineate a diffuse, large (nearly 1000 km long), and persistent (years) haline front which overlies the continental slope in the eastern Bering Sea. The front marks a transition between the waters above the deep basin, where the horizontal salinity gradient is almost zero and the flow is geostrophic, and the waters above the broad shelf, where salinity gradients are large and the flow is tidally dominated. We suggest that the change in mixing from the oceanic regime above the deep basin to the tidal regime over the shelf is responsible for the front. Because our arguments do not depend upon features unique to the Bering Sea slope, similar fronts should be found where freshwater runoff can dominate the density gradient and where strong boundary currents are absent.