A hydrographic cruise on the continental shelf between Chesapeake Bay and Cape Hatteras on the east coast of the United States during the summer of 1990 revealed the presence of a large volume of Gulf Stream water. Gulf Stream water was observed on the shelf between the depths of 10 m and 30 m, and penetrated the shelfbreak front which normally separates the shelf water from slope water and Gulf Stream water. The layer of Gulf Stream water on the shelf extended 60 km north of Cape Hatteras, and reached at least as far shoreward as the 25 m isobath. Velocities of Gulf Stream water in the upper 110 m of the water column along the 100 m isobath indicated a flow of 18 to 25 cm/s directed toward the northwest. The Gulf Stream water on the shelf was associated with low values of fluorescence, transmissivity, and nutrient concentrations relative to adjacent shelf water. The presence of the seasonal stratification during the summer may allow for mid-level penetration of Gulf Stream water onto the continental shelf north of Cape Hatteras. ¿ American Geophysical Union 1992