A brief review is given of the history of the Great Canadian Oil Sands (G.CØS.) project to recover 45,000 bpd of synthetic crude oil from the Athabasca Tar Sands by open pit mining, hot water extraction, coking, and hydrorefining. This paper then discusses the startup and initial operation of the G.CØS. plant. Emphasis is directed toward actual vs. design performance and a general discussion of operating problems. Included in the technical discussion are geological and mechanical problems encountered in mining tar sand, performance of the hot water extraction process, coking of Athabasca bitumen, hydrorefining of coker distillate produced from bitumen, and properties of the finished synthetic crude oil.