ABSTRACT The paper is focused on Slovene and Serbian state socialist experts and their role in the scientific field of researching the Yugoslav national question in the first half of the 1960s, with emphasis on their research and debates regarding the concept of national Yugoslavism. The institutes being examined are the Institute for Ethnic Studies (Inštitut za narodnostna vprašanja, INV) in Ljubljana and the Institute of Social Sciences (Institut društvenih nauka, IDN) in Belgrade. In the early 1960s, Yugoslav soft nation-building reached its peak with the famous Ćosić–Pirjevec debate. The latter coincided with the end of the ‘transitional period’ at INV and its new leadership under Drago Druškovič. Some Serbian lawyers shifted the fight for the establishment of a socialist Yugoslav nation from political debates to the Yugoslav Association for International Law, where the dispute reached a climax in late 1964. With the abandonment of the Yugoslav national idea, IDN prepared an ambitious programme of researching Yugoslav interethnic relations, which would include several institutions from all Yugoslav republics. The League of Communists of Yugoslavia financed research on interethnic relations in Yugoslavia to create ‘correct’ policies with regard to the national question. Huge amounts of data were collected (public opinion polls, newspaper clippings) and analysed by the research institutions mentioned earlier, which often gave expert opinions to leading Communists. In the late 1960s, amateur research and opinion polling conducted by Yugoslav newspapers challenged the monopoly of the Party on the scientific research field of interethnic relations. Thus, in the early 1970s, the Party struggled to retake control.