Economic development and social welfare depend on the existence of effective and efficient infrastructure systems, particularly in health, energy, transportation and water, many of which are developed and managed through Public-Private Partnerships (PPPs). However, empirical evidence suggests some pitfalls in the use of these PPP arrangements. This book addresses these issues, focusing on mostly three key questions: How to improve the robustness of the decision-making process leading to the option of PPP? How to improve contract management as the longest phase of the process? How can contracts be improved to accommodate uncertainty and avoid harmful renegotiations? The authors explore the concept of flexible contracts, the uncertainty modeling for improving the robustness of the decision-making process, and develop an overall framework for effective contract management, along with a comprehensive analysis of current renegotiation patterns. The ultimate goal is to improve the contractual performance, as well as the overall infrastructure management and social welfare.