This article analyzes the unfolding of the controversy over the regulation of the release into the environment of genetically modified organisms (GMOs) in the United States between 1982 and 1990. More precisely, it looks at the interaction between three related sets of practices: i) the events provoked by collective actors presenting themselves as spokespersons for public interest groups, ii) regulatory forms and actions, and, iii) scientific activities and issues in moments of controversy. In doing so, the article goes beyond simplistic dichotomies such as those opposing a rational science to an irrational public, or the equally simplistic picture of corrupt scientists cynically manipulating public opinion by resorting to technical arguments. These simplifications need to be replaced by an analysis which equates controversies to socio-technical episodes grounded in the existence of regulatory agencies maintaining complex relations with scientific intitutions of varying size, scale, and composition, from long-lasting professional organizations to short-lived speciality fields and research fronts. In this perspective, the "public" proves to be an artifact constructed by contending actors in the interstices, and within the jurisdictional terrain, of various regulatory agencies.