This study examines explanations for the success or failure of planning efforts of the 1945 British Labour Government and the French Government of the Fourth Republic. Most conventional views of British postwar planning depict it as hopelessly weak and disorganized while French planning is seen as reasonably well-armed and effectively organized. However, these views reflect excessive attention on purely administrative as well as political–cultural explanations and tend to ignore the critical underlying role of domestic politics and power. The French planning effort was only one element of a broader, relatively uncoordinated collaborative process, carried on among bureaucratic state elites and large industry, which effectively accelerated industrial investment and economic growth. Its success hinged on the inability of organized labour effectively to defend its wage interests within the political structure. In the British case, manipulation of capital markets was only marginally productive given the power and autonomy of the finance sector while the alternative attempt to plan through manpower direction failed due to the ability of organized labour to defend its wage interests in the face of chronic inflation. In each case, the structure of political power was most important in determining the success of the divergent technical approaches to planning.