Rules of Origin (ROO) determine the economic nationality of an imported product. Where margins of trade preferences are higher, ROO tend to be very restrictive and even sometimes dilutes the benefits of such preferences. As the ACP-EU Economic Partnership Agreement (EPA) negotiations enter a critical phase, the devil of the agreement will be in the detail of the impending EPAs ROO. According to the original mandate, EPA is supposed to be concluded by December 2007 and should be development friendly. Yet, the recent EC ROO offer to the ACP countries (Commission Staff Working Document Concerning the Definition of “Originating Products and Methods of Administrative Cooperation”) are seen by commentators as completely undermining the development dimension of EPA. Bearing in mind the current EPA negotiations, Roberto Rios explains how ROO impact the pattern of trade between countries and how they can be development friendly.