Northern Alberta's oil-sand deposits contain some 143 Gt (900 × 109 bbl) of bitumen from which at least 36 Gt (250 × 109 bbl) of marketable light ‘synthetic crude oil’ are expected to be ultimately producible. Representing Canada's largest potential ‘petroleum’ reservoir, and of a size large enough to be compared with the total recoverable oil reserves of the Middle East, these deposits may become the country's principal source of future petroleum supplies. This review briefly describes the geological setting of the oil sands, and the methods by which bitumen can be extracted and upgraded; outlines current and planned commercial projects; and notes some of the factors bearing on future exploitation of the oil sands.