Strategic planning and decision making in the face of uncertainty have always presented a serious challenge to top management, but the present scale of uncertainty is unprecedented. Decision makers used to be able to rely on the past to predict the trends of the future. Now they are increasingly being forced to make important decisions that depend upon highly uncertain external factors for which the past offers little guidance. In all areas of business and government, there is a vital need to understand and implement procedures that enable decision makers to deal more effectively with uncertainty for planning and allocating their organizations' resources. Because of differences in their social, political and economic environments, European and Japanese managers are today affected by many acute areas of uncertainty— such as industrial democracy, floating exchange rates, changing social and political values, growing environmental awareness, government regulation, technological change, pollution control regulation, energy cost, and raw material availability—earlier than their counterparts in the U.S.A. These uncertainties affect not only private sector manufacturing industries, but also financial and service industries as well as nationalized industries and government organizations. This article shows how ineffective methods of dealing with uncertainty can lead to serious mistakes with costly consequences. The cost of overconfidence and people's natural but futile tendency to ignore or to try to eliminate uncertainty is illustrated by the crises seen recently in the world steel and shipbuilding industries. The article then demonstrates how decision analysis procedures that focus directly on the major decision points in the strategic plan enable executives not only to include uncertainty directly in their strategic planning, but also to increase their understanding of the decision process and their ability to communicate the results to others.