In the field of Rare Diseases, patient registries and databases are key instruments for the development of clinical research, improvement of patient care and healthcare planning. They can achieve a sufficient sample size for epidemiological and/or clinical research, to assess feasibility of and facilitate planning of appropriate clinical trials, and support the enrolment of patients to be treated with orphan drugs. Registries of patients treated allow the gathering of evidence on the effectiveness of treatments and possible side effects, since marketing authorisation is often granted when evidence albeit convincing, is limited. The European Registry of Cushing's syndrome (ERCUSYN) database initially funded by the EU, now includes data on over 500 patients. It represents the largest collaboration of endocrine centres in Europe and has potential not only for improving the care of patients with Cushing's syndrome, but also to extend its collaboration into new areas. It may be used as a rare disease registry for an orphan drug to be evaluated, such as a new somatostatin analogue. This academic registry set up before marketing authorization of this new drug as a disease registry, may be liaised to a European Medicines Agency-regulated, industry-required post-marketing surveillance study, to follow safety and efficacy in the long term outcomes in clinical practice conditions. Through the ESE this network may be used to disseminate information and encourage further interaction between endocrinologists across Europe. © 2012 Elsevier Masson SAS.