In these days, due to the increase of general interests in health and environmental concerns, trade disputes involving environment-related trade regulation measures have frequently occurred. Most of these measures, which are aimed at achieving specific policy objectives such as health protection or environment conservation, can be classified as violations of the general principles of GATT/WTO legal system. In general, these environment-related trade regulation measures can be justified based on the general exceptions of `GATT 1994` Article XX, particularly subparagraphs (b) and (g). Those justifiable exceptions are the measures which are necessary to protect human, animal or plant life or health(Article XX(b)) and relating to the conservation of exhaustible natural resources(Article XX(g)). However, even though those measures meet the requirements of Article XX (b) or (g), they should also satisfy the other legitimate conditions provided in the chapeau of the Article XX. These legitimate conditions and scope of both Article XX (b)ㆍ(g) and chapeau have been core issues regarding environment-related trade regulation measures in the international environmental law as well as international trade law. According to the GATT panels and WTO panelsㆍAppellate Body, exceptional trade regulation measures for environmental protection should meet requirements of `necessity` or `relevance.` Basically, these requirements mean that ⅰ) environment-related trade regulation measures should be the least restrictive to international trade, ⅱ) there is not any alternative mean which can be reasonably used, ⅲ) there is somewhat supporting scientific evidence for necessity, ⅳ) there should exist close, reasonable and genuine relation between the measure in question and policy objective, ⅴ) the measures should secure transparency and predictability, and ⅵ) there should be balance of measures and policy objective. In addition, the justification of unilateral and extra-jurisdictional environment-related trade regulation measures will be rejected in principle. However, the recent WTO Appellate Body, have gradually opened the possibility of justification for those measures. Therefore, we should continually keep a close watch on the trends and approach of WTO`s interpretation and application regarding legitimate conditions and scope of environment-related trade regulation measures, in order to avoid unnecessary trade disputes as well as to establish effective regulatory policies to protect health or conserve the environment.