While individually rare, orphan diseases collectively are actually quite common, with an estimated 350 million sufferers worldwide. Since the introduction of the Orphan Drug Act in the US more than 30 years ago, followed by legislation in Japan in the 1990s, and the EU Regulation on Orphan Medicinal Products in 2000, the number of orphan designations has skyrocketed. There are currently around 566 orphan drugs in development, encompassing many diff erent therapeutic areas. Despite the strong financial and regulatory incentives introduced by the legislation, drug development programmes for the treatment of rare diseases still face many challenges. These include the small number of patients available, poor understanding of the disease, difficulties associated with trial design, and challenges with patient enrolment and retention. This paper discusses some of the practical approaches that can be taken to facilitate drug development in this challenging field.