The book provides a new approach to the use of risk assessment as an instrument, describing and characterizing knowledge and lack of knowledge. Knowledge in risk assessment and management aims at presenting research that has been conducted in recent years around these issues, carried out as a part of the Research council of Norway through the Petromaks II program and the project Improved risk assessment to better reflect the knowledge and surprise dimensions . Key features: Presents a new perspective on risk assessments Provides an accessible and concise exposition of a complex topic Numerous cases and examples are provided, with main focus on engineering