Seven determinations of geothermal heat flow were made in the general area of southern Prince Patrick Island in the Canadian Arctic Archipelago. Measurements were made from sea ice in water depths of between 200 and 600 m. The mean heat flow for the two stations on the continental shelf in the Arctic Ocean was 0.46 ± 0.08 μcal cm−2 s−1. The mean heat flow for the five stations in the channels to the east of Mould Bay was 1.46 ± 0.16 μcal cm−2 s−1. The instrument and field methods are described. Errors due to the instrument and to the environment are discussed.