In 2009 the European Commission asked the Member States to develop a strategy to improve the care of rare disease patients by 2013 (2009/C 151/02). In Belgium, recommendations for measures to fill unmet needs of rare disease patients were formulated by the Fund of Rare Diseases and Orphan Drugs at the King Baudouin Foundation. As a result, for 2012-2013, the government provides a budget to work out the implementation of a central rare disease registry collecting a minimum common dataset. Indeed, registration of rare diseases would be highly beneficial to patients, caregivers, authorities, researchers and the general public. Registries can be used e.g. for epidemiological research; incidence, prevalence and survival calculations; quality of patient care, health-care planning and monitoring.Belgian data on rare disease patients are scarce and fragmented. The primary goal is to bring together already existing data (e.g. by extraction from established registries), to harmonize the different initiatives and to start up registration of core data for additional rare diseases. The Orphanet nomenclature of rare diseases will be used as this will allow mapping to the ICD11 in the future.The core dataset will serve epidemiological purposes, including some quality indicators. In the future, also data on orphan drug use will be collected and other administrative or dossier functionalities might be implemented.