The main ice caps on Devon Island, central and northeast Ellesmere Island, and Axel Heiberg Island were sounded using a 620 MHz radar. Ice depths were found to be generally between 300 and 800 m. The bedrock topography is everywhere very irregular. There is a pronounced difference between the thickness, and hence volume, of ice on the east and west sides of the Central Ellesmere and Devon ice caps. The greater thickness on the east sides is attributed to much higher snow accumulation rates there and it is calculated that the asymmetry between the east and west sides began to develop some 8000 years ago. The greater thickness of ice on the ice caps facing Baffin Bay must be considered in any derivation of the dimensions of the Wisconsin ice sheet from maps of isostatic rebound in the Queen Elizabeth Islands. Some of the northwest–southeast tilt of strandlines on Devon and Southern Ellesmere islands can be attributed to the suppression of rebound by these thick ice masses. It is inferred, from the greater symmetry of ice caps in Northern Ellesmere and to a lesser extent Axel Heiberg Island, that the Arctic Ocean is a much less effective moisture source than Baffin Bay.