Following the importance of understanding and asssessing geotechnical hazards, vulnerability and risk, new concepts and techniques of reliability analysis have been developed in the last 20 years. Though widely accepted, application has been slow. This book introduces basic principles and methods of geotechnical risk and reliability and demonstrates their relevance for improved understanding, more effective strategies and better problem-solving skills. Attention is given to the latest developments in the application to geotechnical problems and how reliability analysis and assessment of hazard and risk along with suitable observational approaches can facilitate the management of risk.