One hands, all WTO members have the fundamental right to take sanitary and phytosanitary measures("SPS measures") necessary for the protection of their consumers, animals and plants from health risks. The other hands, members shall ensure that their sanitary and phytosanitary measures do not arbitrarily or unjustifiably discriminate between Members where identical or similar conditions prevail, including between their own territory and that of other Members. Sanitary and phytosanitary measures shall not be applied in a manner which would constitute a disguised restriction on international trade. This obligation under the Agreement on the Application of Sanitary and Phytosanitary Measures (“SPS Agreement”) was to described in Article 5.5. The Article 5.5 indicates that a complaint of violation of this Article must show the presence of three distinct elements. The first element is that the member imposing the measure complained of its own appropriate levels of sanitary protection in several different situations. The second element to be shown is that those levels of protection exhibit arbitrary or unjustifiable differences in their treatment of different situations. The last element requires that the arbitrary or unjustifiable differences result in discrimination or a disguised restriction of international trade. This thesis focus on interpretation of the three element of Article 5 of SPS Agreement, and aims at highlighting a number of lessons to be learnt from the present WTO system concerning distinctions in Levels of Protection.