This article examines how Canada's first national blood donation program originated during World War II. It focuses on the genesis of Charles H. Best's serum project at the University of Toronto, and the federal government's decision in 1940 to sponsor it as the nation's most viable blood banking option. While Best's personal initiatives were crucial, his project's success was also a result of the larger scientific, political, and institutional circumstances of Canadian medicine. The article also analyzes why the federal government gave responsibility for blood collection to the Canadian Red Cross Society. It shows how the organization's traditional association with military medicine, its more recent involvement with community health services (including blood transfusion), and its flexible national structure suited it for this task. Moreover, Ottawa's willingness to assign this role to a volunteer agency was an indication of the structural deficiencies in Canada's primitive health-care system. The decisions of 1940 flowed from the immediate wartime pressures and individual initiatives. They reflected as well the deeper scientific, institutional, and cultural realities of the time.