This article focuses on census policy-making by analysing the decisionmaking processes behind the apparent stability of Brazilian racial categories within a context of multiple changes in racial politics and policies over the last four decades (1970-2010). Empirically, we rely on archival material, survey and census data, as well as key informant interviews with senior technocrats from the Instituto Brasileiro de Geografia e Estatística (Brazilian Institute for Geography and Statistics, IBGE). Our findings show the central role of technocratic actors in shaping and giving meaning to these categories in a context of uncertainty about the most valid approach to measurement. Their role is particularly evident in IBGE's early application of the 'negro' category to the non-white population and repeated rejection of the 'moreno' category. Beyond technical expertise, these census officials navigated various professional, political and ideological motivations. We develop the concept of technocratic compromise to capture census officials' decision-making process and underscore its importance to explaining census policy outcomes.