The article analyses forms of international scientific exchange practised by Polish medical experts around 1900. Applying a transnational historiographical approach it asks whether and how the Polish nation mattered to Polish bacteriologists and epidemiologists travelling abroad or communicating with colleagues internationally. It shows that in the 1880s and 1890s the Warsaw bacteriologist Odo Bujwid rarely connected his scientific knowledge to Polish national causes but rather benefited from imperial structures. What was more, he transcended the borders between the two nationalised bacteriological thought styles of Louis Pasteur on the one hand and Robert Koch on the other. Bujwid thus eluded a clear link between science and nationalism. His practices of international scientific exchange can be called ‘transnational’. When a Polish state was re-established in 1918 bacteriology and epidemiology became closely entwined with Polish state- and nation-building. Polish medical scientists now worked for Polish state institutions and acted as state representatives in the international arena. International exchange and border-crossing scientific mobility now served, first of all, to underline Polish statehood and to present it as a modern and civilised country. These practices of international scientific exchange can be described as ‘Olympic Internationalism’.