Crustal structure beneath the transition from the Coast belt to the Intermontane superterrane of the northern Canadian Cordillera is interpreted from the inversion of refraction and wide-angle reflection seismic data. The profile traverses an accretionary suture zone (Coast Plutonic Complex) to continental crust deformed by the transpressive collision (Stikine terrane). Using data acquired by the Accrete onshore/offshore experiment and by a partially overlapping Lithoprobe onshore experiment, P wave travel time inversion and forward amplitude modeling are employed to determine crustal velocity structure. The model exhibits a well-defined transition throughout the crust that distinguishes the Coast Plutonic Complex (CPC) from Stikinia. Average crustal velocities beneath the CPC (6.45 km/s) are considerably faster than those beneath Stikinia (6.25 km/s). Crustal thickness also changes across the transition; thin crust beneath the Coast belt (30--32 km) thickens beneath Stikinia (35--37 km). The observations within the Coast belt are consistent with a tectonic history most recently dominated by extensional deformation. Primary structural control could be associated with either Neogene extension and/or the processes that are responsible for exhuming the Coast belt during the early Paleogene and have been inferred from geological studies. Slow mantle velocities (7.8--7.9 km/s) beneath the entire profile are indicative of high upper mantle temperatures. Comparison with the southern Cordilleran Coast belt reveals similar velocity structure within the massive plutonic complexes. However, substantial differences between the northern and southern Coast belts emphasize along-strike variations in terranes, orogen geometry and postorogenic tectonics. ¿ 2000 American Geophysical Union