Abstract This thesis examines international commercial contracts from the perspective of the United Nations Convention on Contracts for the International Sale of Goods 1980 (CISG) rules. It is noted that the different national legal systems are the most important factors that contribute to obstruct the development of international business relations between countries in particular for the conclusion of contract, due to the huge problems arising from the governing law. For the reason of many diversity of domestic laws, CISG can be a proper law for governing contract among contracting states. The first chapter in this study is about CISG in general, including the historical background and spheres of its application. The second chapter concentrates on the formation of contract under the CISG rules and an offer which the beginning phase of the conclusion of contract. Finally, the third chapter examines acceptance and modification of contract which is the complementary chapter of the second chapter.