In his seminal article ”Knowledge in transit” James Secord made a case for the study of the circulation of knowledge, and he pointed out the critical yet neglected role of how scientific results are made public. “It is amazing that we lack a good general history of the protocols and procedures for announcing a discovery in different periods” (Secord 2004: 667). Communication, popularization and circulation of scientific results can come in many forms: scientific conferences, scientific journals, books, museums, exhibitions etcetera. This paper emphasizes one crucial aspect: the role of the mass media – and more exactly – the role of press conferences. The case that is discussed is large-scale assessments conducted by The International Association for the Evaluation of Educational Achievement (IEA) in the 1960s and 1970s, an organization which expressed a great interest, but also a great ambivalence, towards the media. By analyzing IEA’s contradictory attitude towards the media, the ambition is to shed new light not only on how and why scientific knowledge circulates but also on the early history of large-scale assessments. The early history of IEA demonstrates that the mass media was an important, yet, problematic, ally. The question that this paper addresses is about the roots of this ambivalent attitude. Why was media considered so important, and why was it so problematic? Or, in other words, which messages were important and doable to disseminate through the media, and which distortions of the message due to the media were detected? Drawing on research on audiences/publics and the history of social science (e.g. Ekström 2004, Cooter & Pumfrey 1994) the paper discusses how social science is made public, and the relationship between social science, media and the public. By adding the phenomena of press conferences, the paper introduces a neglected theme in the history of social science. Press conferences haven’t been studied much, not even in the realm of political communication where it arguably plays a more prominent role.