Wide-angle reflection/refraction seismic data were acquired on a 450-km-long transect in southern Baffin Bay extending from Baffin Island to Greenland. Dense airgun shots were recorded on 22 ocean bottom seismometers. A P wave velocity model was developed from forward and inverse modeling of the observed travel times. Beneath the Baffin Island shelf, a three-layered continental crust is observed with velocities of 5.5 to 6.9 km/s. Typical for transform margins, there is a sharp transition between continental and oceanic crust. Off Baffin Island, 7-km-thick oceanic crust is interpreted to lie in a major transform fault identified on the gravity map. Beneath the deep Baffin Bay basin, 9-km-thick oceanic crust is encountered but thins to 6 km within an assumed fracture zone. The thicker than normal oceanic crust indicates an ample magma supply, possibly related to melt extracted from a mantle plume. Seaward of the Greenland continental crust, 20-km-thick igneous crust (6.3 to 7.3 km/s) is encountered in a 25 km-wide zone interpreted as a leaky transform fault that can be correlated southward through Davis Strait. The igneous crust is bounded by a 20-km wide basin to the west, underlain by 4-km thick crust of unknown affinity. This structure is probably associated with transform movements. A high-velocity lower crustal layer (7.1 km/s) of 8 km thickness is indicated beneath the Greenland crust and can be correlated into the adjacent thick igneous crust. Both the thick igneous and Greenland crust are covered by up to 4 km of Paleogene volcanics (5.2 to 5.7 km/s).