The number of 'transnational' EU-patients, i.e. EU-citizens receiving medical treatment in another country than their working state--where they contribute for social security--is growing steadily. This article describes the EU and member states' rules governing the reimbursement of the expenses for medical treatment received abroad, for the case where patients travel abroad with the sole purpose of medical care in the framework of the national health insurance (treatment authorised by E112-form). It is illustrated that some countries' national rules comply with the EU-rules, a number of countries apply stricter rules, while other EU-members have established legislation that is more favourable for their citizens, than the EU-rules. Furthermore, the financial burden of treatment abroad also differs widely, since some countries reimburse travel and living expenses for the patient, and sometimes also for an accompanying person, while other countries do not provide such reimbursements. The article concludes with some policy implications.