The geometry and distribution of Mesozoic rift basins off Newfoundland and Nova Scotia are controlled by the interaction of tensional stress fields with pre-existing crustal structure. Reactivation of the structural boundary between the Avalon and Meguma terranes from the Middle Triassic to Early Cretaceous is expressed in a series of sinistral strike-slip basins that contain spectacular diapiric structures. Different basin geometries characterize the terrane interiors. The basin-forming faults of the composite Scotian basin are long and sinuous. Large amounts of extension were accommodated by dip-slip and oblique-slip processes along a system of en echelon and intersecting faults and relay ramps. Ocean opening occurred in the Middle Jurassic after a single episode of extension. The Grand Banks and the Orphan basin were dominated by dip-slip extension. Prominent transfer faults separate different extensional tracts and accommodate different levels and polarities of detachment. The very deep Jeanne d'Arc basin formed above the deepest level of detachment. Late Callovian to Aptian extension dominated the central Grand Banks where the post-rift sequence is thin. Orphan basin was formed largely by Late Cretaceous-early Tertiary extension.