This paper focuses on the issues facing Irish drug users who have migrated to Britain. The main finding is that a number of changes in relation to drug use occur as a result of migration itself. These are both harm increasing and harm reducing, but a majority of respondents self-reported harm increasing changes in drug use particularly in relation to HIV infection. Irish drug users have close networks of friends and relatives that they can access when they come to Britain. However, there is evidence that they are reluctant to approach services. When they did so Irish drug users travelled long distances in London to go to services that were known to work with their community. Together with the multiplicity of problems associated with migration that are described in this paper, the findings show that Irish drug users are a highly vulnerable group within the British drug-using population.