This thesis is concerned primarily with assessing the implications of post-Cold War changes in the United States defence market and defence industrial base for Canadian defence firms and for the Canada-United States defence economic relationship. It is divided into three main parts. The first part traces the evolution of the Canada-United States defence economic relationship from the Ogdensburg Declaration of 1940 to the establishment of the North American Defence Industrial Base Organization (NADIBO) in 1987. The second part looks at the period since the end of the Cold War and, more specifically, at the various changes in US defence industrial policies and corporate strategies that have taken place during this period. The third and final part of the thesis explores the implications of these changes, first, for Canadian defence firms and, second, for the Canada-United States defence economic relationship. Broadly speaking, this thesis makes two arguments. The first is that post-Cold War changes in the United States defence market and defence industrial base will have a major impact on both the number and the types of opportunities available to Canadian defence firms in the American market. The second is that these changes--and, in particular, the growing tendency of the US government to view defence production and trade in economic as well as in military and political terms--may also have important implications for the established pattern of defence economic relations between Canada and the United States. However, despite these implications, this thesis contends that the strong political, economic, and military ties between the two countries should prevent any serious breakdown of the bilateral relationship.