Study describes the seismic velocity structure of Makarov Basin and adjacent Alpha Ridge, Arctic Ocean. Velocities from deep sedimentary layers in Makarov Basin are relatively fast. The crustal structure of Alpha Ridge resembles thick igneous crust. There is little lateral change in crustal velocities between Alpha Ridge and Makarov Basin. The crustal transition from Makarov Basin to Lomonosov Ridge is consistent with strike-slip tectonics.