This paper examines the politics and practices of drug evaluation in Brazil. It traces the history of AIDS activists' influence on the organization of modern clinical trials and their scientific rationale. Using the Merck indinavir trial as a case study, the authors discuss how organized civil society has developed strategies to intervene in the course of drug evaluation trials, shaping them according to its own interests. Adopting translation sociology as the theoretical framework, the paper describes and analyzes the strategies used by activists from "Grupo PelaVidda/SP" (an AIDS NGO) to build a consensus concerning indinavir monotherapy's lack of efficacy. The study considers the several regulatory forums involved in dealing with the controversy during the trial period.