An investigation of the detailed morphology of Wilmington and Baltimore canyons reveals that their salient features and inferred history are very similar. Both canyons trend predominantly southeastward, but the heads display a north-trending hook termination on the shelf. Abrupt alterations in the axial trend of each canyon occur at roughly equivalent axial distances and are accompanied by sharp changes in axial gradient and in the geometry of the canyon profile. The shorter length, lower axial gradient, and less acute profiles of Baltimore canyon indicate that it is morphologically more mature than Wilmington canyon. Continuous seismic reflection profiles in this region have penetrated more than 1 km of sediment, Tertiary and Quaternary in age, but including reflector zones of probable Upper Cretaceous age near the base. Axial faulting, detected only in the north-trending part of Wilmington canyon head, may be linked with Quaternary marginal downwarping. Buried channels occur below the shelf adjacent to tjhe heads of Wilmington and Baltimore canyons and indicate that southeast-trending portions of both canyons were initiated by drainage emanating from the vicinity of Delaware Bay during a late Tertiary lowstand. The north-hooked, shallow portion of each canyon head was subsequently excavated by a glacially enhanced, south-flowing drainage system during Pleistocene lowstands. The subsequent history of the canyon heads involves episodes of filling and reexcavation, including the formation of two widespread erosional benches which correspond to the Nicholls and Franklin shores first recognized in the Hudson canyon region. Large slumped masses on the lower continental slope involve the three groups of reflectors detected below the slope and the upper continental rise. The deepest of these reflector zones-of probable Upper Cretaceous/lower Tertiary age-represents an ancestral abyssal plain or lower continental rise surface, and onlap by upper rise sediments has shifted the slope-rise junction westward by at least 12 km since the lower Tertiary. In the same period, the margin of the continental terrace has been moved to the east by at least 8 km. Subbottom reflectors on the lower slope and upper rise are involved in a number of undulations superimposed upon a basal interface which is itself broadly undulatory. Originating during the Tertiary epoch as a topographic depression on the upper rise, Baltimore valley has acquired its present form through several cycles of erosion and deposition but is at present inactive. Wilmington valley displays a similar complex history, but the presence of a narrow, active channel within the valley suggests that this feature is currently funneling sediment downslope from the shelf and across the upper rise.