Abstract: A thermosyphon for removing heat from a permafrost foundation, the invent can be installed in a frozen foundation with an evaporator section disposed either horizontally or with a negative (up) slope, thereby allowing the evaporator section of the thermosyphon to be buried in a more shallow location of the foundation than is possible with conventional thermosyphon devices. The thermosyphon of the invention has a condensate collection ring near the lowest point but higher than any point in the evaporator of a condenser section which extends above the permafrost foundation and into heat exchange contact with low-temperature above-ground air. Condensate formed in the condenser section by heat exchange with the air is collected in the collection ring and ducted through a condensate return tube to a desirable location within the evaporator section, usually the extreme distal end thereof.