This thesis investigates Zigenarundersökningen [the Gypsy study] – a socio-medical study of Swedish Roma conducted in 1962-1965. The Study was financed by the National Labour Market Board, which sought scientific information on every adult Roma citizen in order to plan for targeted authority interventions. The socio-medical team used a number of different medical and social techniques, drawing together different kinds of data – from the molecular to the social level – and adding “objective” records from public institutions, which resulted in the creation of detailed and voluminous individual case files. On the basis of these files, the public health specialist John Takman in charge of the socio-medical examinations formulated a professional opinion on each individual and family. During the execution of the study, new scientific and social questions were articulated, resulting in that the originally limited investigation concerning only a smaller group of Roma citizens evolved into a comprehensive research project covering all people identified as Swedish Roma. In this thesis, this expansion is analysed using methodological tools from Science and Technology Studies that focus on the reflexivity between the goals of scientific actors, and the social conditions and problematisations that surround them. In this way, science and policy mutually influence each other in situated practices, which also involves the drawing of scientific boundaries that serve to establish epistemic authority.   Departing from Engin F. Isin’s theory on social citizenship, and its alterities, as constituted in contingent and contextualised social practices, and from Franca Iacovetta’s study of Canadian gatekeepers’ work in cold-war Canada, the thesis investigates how the, with time, increasing and more comprehensive activities of experts and professionals created new dimensions of citizenship. Against this background, the thesis draws the conclusion that the scientific-political examinations of problematised citizenship and citizens in Sweden in the 1960’s, while defining deviance, also defined normality. This implies, furthermore, that scientific measurements and classifications of alterity contributed to constituting those measuring and classifying – the experts and professionals – as virtuous citizens, in accordance with contemporary norms of professionalism and expertise, while the Roma were continually constructed as problematic citizens. Hence, scientific-political activities concerning Swedish Roma in the 1960’s created new spaces of social citizenship, where the contents of both normality and deviance were nuanced and (re)defined.