Josephine Butler's campaigns against the state regulation of prostitution have been studied almost exclusively in the anglophone and imperial context. Research on the International Abolitionist Federation, which she founded in 1875 and supported until her death in 1906, places these campaigns in a new perspective, demonstrating the importance she attached to the issue in Europe. This article reports on findings at the half-way stage of a project funded by the Leverhulme Foundation under its ‘International Academic Networks’ programme. The strains and contradictions revealed in the correspondence and proceedings of the Federation illuminate cultural and social differences between countries often summarized simplistically as ‘the west’. The influence exercised by Butler, especially over a new generation of French and German feminists in the 1890s, throws new light both on her own career and on the work which these women undertook in the League of Nations in the period between the two world wars.