In the past, four different modes of origin have been proposed for the Laurentian Channel: structural, subaerial erosion, glacial erosion, and erosion by turbidity currents. To extend our knowledge of the outer part of the Laurentian Channel and further elucidate the problem of the origin of this important topographical feature, we have employed seismic-reflection profiling techniques.Two significant sub-bottom surfaces are recognized from the profiles: (1) A more or less smooth glacial pavement across Carboniferous, Cretaceous, and Tertiary (?) strata that conforms closely to the shape of the present sea floor; (2) an older, irregular, erosional surface cut into Carboniferous and Cretaceous rocks. These channels are infilled with Tertiary sediments.Based on the evidence gained from our interpretation of the seismic records, it appears likely that the outer channel is essentially a product of subaerial and subsequent glacial erosion. It does not appear to be structurally controlled, nor does it appear to have been formed by turbidity currents.