The configuration of sedimentary strata revealed by continuous seismic-reflection profiles over submarine canyons on the upper continental slope off Cape Hatteras is best explained by the hy pothesis of composite origin of submarine canyons. The canyons were originally incised into a post-Miocene (?) surface of unconformity. The intercanyon areas were constructed by deposition of sediment up to several hundred meters thick forming the canyon walls while the canyons were maintained by sediment removal processes over the sites of original incision. Canyon heads are presently buried under a smooth sediment cover which extends from the shelf break at about 90 m down to about 400 m below sea level, where the canyons emerge from the cover. The depth of emergence of canyons approximately coincides with the inferred level of no motion between the northeast-flowing Florida Current and the southwest-flowing Western Boundary Undercurrent.