Permafrost, or perennially frozen ground, occurs widely throughout the northern half of Canada. Experience has shown that special design and construction techniques are required for building on permafrost in order to avoid disturbing the delicate thermal balance that preserves the frozen ground. The state of knowledge is reviewed with respect to site investigations, foundation designs, water supply and sewage disposal, the construction of transportation facilities, and the influence of surface flooding, drainage and other disturbances on the ground thermal regime. Attention is drawn to an extensive literature and research needs are outlined.