Citizens of the United Kingdom have voted to leave the European Union. The question remains what effect Brexit, once implemented, will have on the United Kingdom, the European Union and third countries. In this paper, we focus on the potential impacts on agricultural exporters. Many countries have preferential trading arrangements with the European Union, and hence the United Kingdom. As a lapsed member of the European Union, the United Kingdom could remove these preferences and impose MFN rates on all WTO members, or it could remove its tariffs altogether, allowing non-ACP countries to compete with preference beneficiaries. This would allow, for example, Brazil, Thailand and Australia to supply sugar to the United Kingdom in competition with Mauritius, Zimbabwe, Fiji and several other developing countries. This would have a negative impact on these countries. Similar concerns apply to beef and dairy products. Although the terms and condition of exit have not yet been negotiated, the potential effects are quantified with a global general equilibrium model. The impacts of third countries depend on the approach taken by the United Kingdom.