Project-oriented organizations face environments differing in complexity, with different degrees of maturity needed to manage uncertainty. In this chapter, the authors analyze where, when, and by whom structure or autonomy should be made use of in project-oriented organizations, and which kinds of structure and autonomy are appropriate for dealing with complex, uncertain situations and unexpected events. After a short discussion of project management maturity models, the authors investigate the concepts of risk, uncertainty, and the unexpected based on organization theory inspired by decision-making concepts and systems theory. Implications for uncertainty management and managing the unexpected on project and organizational level and high-reliability practices are then derived with a critical look at recent approaches of project management adhocracy.