歐洲共同體及其成員國都是世界貿易組織的會員，這種複雜的情況，對第三國或對EC本身都帶來了若干難題。就實際運作來說，在世界貿易體系下，從提議談判到締結協定，EC各機構及成員國間「分工合作」的機制值得了解。 在談判階段，執委會是發起者也是執行者，理事會與歐洲議會則扮演把關及建議的角色。另外，「一三三委員會」（原一一三委員會）與「談判指令」對於談判方向的引導也有重要的影響，在烏拉圭回合後的新一回合談判，即所謂千禧年回合中仍將有其作用。以執委會為代表「歐洲共同體及其成員國」對外談判的唯一代表，及歐洲共同體須以「單一行為主體」參與WTO，已在EC內部漸成共識。理事會在一九九九年十月提出的「WTO第三次部長會議之預備文件」中，確認了這一點。 在締約階段，以歐洲共同體條約第三○○條（原第二二八條）為基礎，執委會、歐洲議會、理事會分別負責締約提議、同意締約、決定締約之任務。理事會94/800/EC決定，樹立了締約決定的模式，其後的理事會締約決，大致皆遵循其模式。 歐洲共同體在簽署世界貿易組織設立協定前夕，出現對外貿易權限爭議，遂有歐洲法院1/94意見之提出，但這份文件遭到了不少批評。阿姆斯特丹條約新增歐洲共同體條約第一三三條第五項（原第一一三條第五項），係針對1/94意見之後遺症所作的補救，然而此一新增條款卻始終未被使用。二○○○十月通過的尼斯條約草案，再對第一三三條作出大幅修正，未來尼斯條約生效後，新條文對於EC談判及締約行為之影響如何，值得持續觀察。

　　　　　The European Community has established mechanisms of collaboration as per the agreement reached during World Trade Organization negotiations. During negotiations, the Commission initiated and executed while the Council and the European Parliament played the roles of gatekeeper and consultant. The so-called "133 Committee" and "Negotiating Directives" also played a crucial guiding role during the negotiations and will continue to do so in the Millennium Round negotiation. The Community shall act as a "single undertaking" under the world trading system and the Commission will be the sole negotiator for "the Community and its Members," as confirmed by the Council's "Preparation of the Third WTO Ministerial Conference Council conclusions" on 25th October 1999. During the conclusion stage, the Commission, the Council, and the European parliament will take different responsibilities under article 300 (ex article 228) of the EC Treaty. As far as the Council is concerned. Council Decision 90/800/EC has set a model for the forthcoming conduct. However, the future impact of the newly revised article 133, which was amended and expanded under the Amsterdam Treaty of 1997 and the (Draft) Nice Treaty of 2000, should be further studied.