Design and construction of projects is complex endeavor that requires the coordination of a multitude of human, physical, and natural resources. The technical design and construction complexities are frequently outweighed by the uncertainties and risks with the social, financial, and political aspects of the projects. To address these risks and uncertainties, project participants have turned to a series of cost and schedule risk management tools over the past 50 years. This paper summarizes the evolution of probabilistic cost estimating and scheduling tools. It also provides examples of applications on complex projects from the US Department of Energy, the US Federal Highway Administration/Washington State Department of Transportation, the Panama Canal Authority, and the international ITER fusion generator. The paper concludes with a discussion of the remaining cost and schedule risk management challenges, which inhibit project participants from achieving their project performance goals.