世界贸易组织的多边贸易规则，明确承认发展中国家尤其是最不发达国家的特殊利益和要求，在实施期限和义务水平上，都对发展中国家尤其是最不发达国家作出了特殊的安排。
一、特殊差别待遇与普遍优惠待遇的确立
1947年成立初期的GATT的23个缔约方中，有11个发展中国家。但是1947年总协定最初并没有关于发展中国家的特殊规定。1955年关贸总协定作了第一次重要的修订，可看作是特殊和差别待遇的起源。这就是第18条关于发展中国家的特殊规定。GATT第18条题为政府对经济发展的援助，中心思想是发展中国家有更多的自由使用数量限制及其他限制措施保护其幼稚工业和国际收支平衡。具体内容是：
（1）关税再谈判，第18条A节规定，经济上处于发展初期阶段的缔约方（现为WTO成员）为加速某一特定工业建立以提高人民生活水平，可以较为灵活地修改或撤销关税减让表中的某些减让，但需通知缔约方全体（现应为货物贸易理事会）成员，并与有利害关系的其他成员谈判。如达成协议，受损失的成员有权对采取措施的成员实行对等减让。
Section A：7.（a）If a contracting party coming within the scope of paragraph 4 （a） of this Article considers it desirable, in order to promote the establishment of a particular industry* with a view to raising the general standard of living of its people, to modify or withdraw a concession included in the appropriate Schedule annexed to this Agreement, it shall notify the CONTRACTING PARTIES to this effect and enter into negotiations with any contracting party with which such concession was initially negotiated, and with any other contracting party determined by the CONTRACTING PARTIES to have a substantial interest therein. If agreement is reached between such contracting parties concerned, they shall be free to modify or withdraw concessions under the appropriate Schedules to this Agreement in order to give effect to such agreement, including any compensatory adjustments involved.