This comprehensive chapter documents, from a management perspective, the knowledge base on risk assessments and risk management. The previous chapter in the book is a companion article that provides the scientific foundation for the concepts and terminology used by Cleaves and Haynes. In this chapter, Cleaves and Haynes provide a framework for considering the uncertain outcomes of management actions and natural events. They review uncertainty and risk management principles, review strategies for adjusting ecosystem risks, and provide suggestions for fitting uncertainty management into organizational cultures. They begin with a definition of terms. For example, uncertainty is described as a set of unknowns, based on a combination of ambiguity, knowledge gaps, and variation in natural and human processes. Risk, which is the likelihood of an adverse effect or loss, reflects the human assessment of value. Risk assessment is used to estimate the probabilities and magnitudes of the effects and consequences (gains and losses) of stressors on natural resources. Risk adjustment is an effort to modify, mitigate, or respond to stressors in a way that holds consequences to acceptable levels. Risk characterization is a summary of the risk, its nature and context, and how it might be adjusted. Risk communication is an exchange of information about a particular risk or group of risks. Most of the article describes the risk management cycle, including detailed discussions of hazard identification, risk assessment, evaluation, adjustment, implementation, and monitoring. The authors use case studies to illustrate issues of endpoint objectives, expert judgment, cost/benefit trade-offs, risk adjustment instruments (for example, performance standards, regulations, incentives), and shifting risk profiles. They also describe an example of a USDA Forest Service Decision Protocol designed for use by Interdisciplinary Teams. The final sections address risk communication, the adoption of a risk management paradigm, and risk-based thinking in organizations. The authors recognize that, rather than documenting decisions already made, good risk assessments expose many incorrect and unfounded assumptions, stimulate learning, and improve decision making. They emphasize embracing uncertainty, accepting risk, using failures to stimulate learning, using probabilities for risk assessment, viewing risk management as iterative and adaptive, ensuring that risk assessments are actually applied to decision making, and developing organizational characteristics that promote risk-based thinking.