This study focuses on the role of public health experts in the contemporary health sector reform process. The authors discuss the issue based on the case of Brazil and Mexico, where a group of public health specialists have oriented their participation to influence the conflict concerning health policy reform in the respective countries. One approach has been to develop a new cognitive framework for technical health sector reform projects viewed as policy proposals with technical content. The purpose is to demonstrate how these specialists have managed to influence the national debate over health sector reform when the technical and scientific discussion leaves the academic sphere and reaches the social and political realm. The authors contend that this occurs because such technical and scientific knowledge has been postulated (independently of its intrinsic value) as a political and ideological alternative platform for sustaining a health sector reform proposal which, once transformed into a policy project, has served to aggregate certain political and social forces.