The author emphasizes the significance of enzootic bovine leukosis in Canada. He describes in detail diagnostic methods, various types of the disease and methods of transmission. Various aspects of the disease in Canada are compared with those in other countries. Prevention and control are discussed in a Canadian context and include the current policies of the Government of Canada in relationship to this disease. The possibility of developing a certification program for herds free of the disease is also discussed. The paper includes incidence in various parts of Canada.