We wish to propose a session on what we call scientific cosmopolitanism. The proposal grows from a group of papers that were presented at the Barcelona congress on the movement of scientists and of scientific knowledge and practices within Europe since the sixteenth century. In Barcelona, the papers focussed on travels between countries and relatively brief stays abroad. The Athens congress provides the opportunity for developing a rather different perspective, focussing on scientists who have chosen to settle away from their own countries, either permanently or for extended periods. The cases of Tycho Brahe and Kepler, both of whom resided in Prague, are well known. So too are those of Herschel in England and Burkhardt de Gotha in Paris. And there are many other instances. The motives that led to such decisions to work abroad might include, among others, congenial living and working conditions or difficulties of a religious or ideological kind. The purpose of the papers in this session will be to discuss key examples, with a view to determining the similarities and differences between them and whether or not the decisions reflected a free choice or pressures that made expatriation a necessity.