Indeks : Indeks ; This book is concerned wiht the legal problems of long-term contractual relationships. It considers the particular concept of change in circumstance, namely the economic change as a result of outbreak of war, export and import prohibition and economic depression, which upset intensely the contrctual equilibrium and the economic balance of obligations during the performance of contract. It provides a comparative analysis of the effect of change in circumstances in english, american,indian and iranian law. This book is intended to provide a legal apporoach not only for law students, lawyers, judgesand tribunal members, but also for those wishing to acquiri a knowledge of this important subject. This book bisides theoretical analysis and legal viewpoints contains many references to cases and statutes, all of which are listed in covenient tables. Written in a clear and lucid manner, the book includes the background of subject and main problem, legal nature and scope of the theory of changed circumstances, a comparison between the theory in question and the similar theories such as " force majeure", "frustation", "Impracticability","hardship",etc.