This paper investigates the extent of overseas migration by British chemists over the period 1887-1971. Notwithstanding the "brain drain" alarms of the 1960s, overseas employment was characteristic of some 19% of British chemists' careers throughout our period, though its nature changed considerably. Our study examines the overseas employment histories of four cohorts of members of the [Royal] Institute of Chemistry in the "Chemists' Database" at the Open University. Those employed abroad were not only highly qualified but also both geographically mobile and occupationally versatile. Over the period, the pattern of chemists' migration was broadly similar to that of British migration trends more generally. Except in the interwar years, chemists' rate of migration was relatively constant. However, the length of time they spent abroad declined markedly over the period: long-term migration became less characteristic than short-term overseas employment for purposes of career development. From the late nineteenth century, British chemists staffed the Empire, but also found employment in the expanding US economy. After 1945, chemists' destinations shifted more markedly towards North America, including Canada, and later also to Europe. Our work thus provides a new perspective on the dynamics of scientists' migration and contributes to studies on the brain drain. (Contains 6 tables and 94 footnotes.)