Aeromagnetic data have been used as a basis for making inferences about the geologic structure and evolution of the Arctic Ocean basin. The Alpha and Nansen ridges produce magnetic profiles which show axial symmetry and appear to correlate with profiles from the flanks of other well-documented ridges in the Greenland and Norwegian Seas. A quantitative attempt has been made to verify these correlations, which infer that the Alpha Cordillera became inactive 40 m.y. ago, when the locus of rifting shifted to the Nansen Ridge. The lack of magnetic disturbance associated with the Lomonosov Ridge is interpreted to indicate a section of the former Eurasian continental margin that was translated into the Arctic basin by sea-floor spreading along the Nansen Ridge axis. Within the C nada basin there is a thickening of sedimentary rocks from the Asian continental margin toward the Canadian Arctic Archipelago. Thickness of the sedimentary sequence in the Makarov basin is estimated to be approximately 1 km--almost twice that of the younger Fram basin.