Chapter 1: This chapter introduces the book and summarises the contents of each part. It states a hypothesis that a new principle of pacta sunt servanda bona fide, based on relational contract theory, is emerging in international trade, where hardship issues arise in performing long-term relational supply contracts. The main proposition is that in the context of hardship, the parties to a long-term relational supply contract have a duty to renegotiate the contract unless there is a ''compelling reason'' not to do so. Additionally, the judges or arbitrators have the power to adapt the contract based on good faith, the relational nature, and the characteristics of the contract. Where there is a complete breakdown of the ongoing contract relationship or the adaptation will cause one or the adaptation will rewrite the contract, the judges or arbitrators have the power to terminate it. Chapter 5: Chapter Five will first address the concrete manifestations of good faith in long-term contracts under the UNIDROIT Principles. It will then identify the gaps and vagueness in the rules underlying the UNIDROIT Principles. Recognising that the book''s ultimate goal is not to design a totally new set of rules in respect of hardship, this chapter will present suggestions on how to improve the quality, and promote the application of, the hardship rules provided by the UNIDROIT Principles. It will suggest how to address the shortcomings and dispel the vagueness surround the hardship issue from both substantive and procedural perspectives. This chapter also proposes a double-construction approach and suggests a list of factors that should be taken into account by the courts or arbitral tribunals in determining whether the parties have acted in good faith.