This book explores a set of moral questions about the brain drain, or the emigration of skilled individuals from one state to another. It asks which duties, if any, the main actors involved in the brain drain owe to each other, in particular whether skilled individuals and the states to which they might emigrate (receiving states) owe duties to people who remain in home states. To what extent do skilled people in low-income states have a duty to stay and work there? Must they transfer to their home state some of the income they earn while working abroad? Must receiving states share with home states some of the gains they obtain as a result of the brain drain? Must states avoid certain kinds of policies in order to recruit skilled people from abroad, such as, for example, policies that offer them tax incentives or preferential tax treatment? After critically evaluating a range of alternative arguments for regulating the brain drain, the book sets out and defends an argument that centres on the idea of exploitation. It shows the various ways in which skilled emigrants, and the states that receive them, gain at the expense of people who remain in home states and how this can amount to exploitation. To avert or redress this exploitation, skilled emigrants can incur duties to transfer resources to their home states. Receiving states can also incur duties necessary for averting or redressing their exploitation of home states, including duties to transfer resources to home states, and duties to avoid using tax incentives or preferential tax treatment as means of recruiting skilled immigrants.