This paper examines an early phase of the controversy over the hazards of recombinant DNA technology in the United States in the period 1976-78, during which agreement was reached within the biomedical community that these hazards were minimal. The proceedings of three scientific meetings that are generally agreed to have been central events in the emergence of this new perception of recombinant DNA hazards are examined. Techniques previously used to examine policy making on non-technical issues are applied here to analyze the formation of this scientific consensus. These techniques are used to show how certain social characteristics of the meetings-the sponsorship and organization of the meetings, informal processes affecting the scope of the proceedings, and the dissemination of the results-acted as `social filters' for the complex set of perceptions of recombinant DNA hazards with which the scientific community started. In contrast to the received view of the recombinant DNA controversy, according to which the issue was resolved at a technical level, this paper argues that social dimensions of the decision process were crucial to the outcome.