Recent decades of years have seen major development in both areas of international trade and development. In theory, international free trade and protection of the environment, two values that are absolutely essential to the well being of mankind could be developed hand in hand in a harmony. However, given the world's current political and economic systems, conflict between international trade and environmental protection seems to grow increasingly since the end of the last century. This thesis is mainly a study of contemporary issues of conflict between trade liberalization and protection of the environment with a specific reference to the position of developing and least developed countries. The primary objective of this research project is to seek a balance, to some degree, between trade liberalization and sustainable development of the environment at the international level. The second chapter elaborates the evolution of the issue of environment in the international trade regime. It states that a great deal of uncertainty remains with regard to the use the rules relating to the environment under the WTO regime, as well as the interpretation of some such rules by the dispute settlement body, which thus becomes a great potential for conflicts between developed countries and their developing/least developed trading partners. The third chapter focuses on the trade-related measures in international environmental law. Analyzing some key trade measures pursuant to the Multilateral Environmental Agreements, it shows that there is a potential incompatibility with those obligations under MEAs and international trade rules, because those MEAs obligations imposed on the Party countries, as well as some on the Non-Party countries that are much more trade restrictive, do affect free trade at the international level, especially to developing and least developed countries. The fourth chapter sets forth contemporary issues of conflict between international trade and environment, by elaborating conflict of norms and conflict of jurisdictions relating to trade measures taken pursuant to MEAS and WTO rules. Based on the discussions about various approaches for reconciling those conflicts at the international level, this chapter discovers that up to now, the special situations and needs of developing and least developed countries have not been attached enough importance to during the negotiations at the international level with regard to dealing with the relationship between the trade measures taken pursuant to MEAs and WTO rules. The fifth chapter intensively makes an analysis of the contemporary issues of conflict between international trade and environment with a specific reference to the position of developing and least developed countries. Not only in the process of making the rules that exert effects on international trade and environment, but also in the process of implementing such rules, developing and least developed countries are treated in a disadvantageous position, compared with their developed counterparts. Moreover, "green trade barrier" is increasingly becoming a weapon that restricts trade liberalization and harms the development of the developing and least developed countries in international trade. In addition, the real situation of giving special treatment to developing and least developed countries at the international level is still unsatisfactory. Those developing and least developed countries, in fact, fail to obtain special treatment effectively and properly in the fields of international trade and environment. Finally, the last chapter concludes that with all the contemporary issues of conflict between international trade liberalization and protection of the environment, the special position of developing and least developed countries is not addressed effectively.