BACKGROUND: There are differences across the world in the definitions used to classify an orphan drug (OD), especially with respect to the prevalence of the disease justifying the orphan status and, the estimation of the population affected by the disease.   OBJECTIVE: To identify the number of medicines which have been granted orphan designation in the United States (US) and European Union (EU), and analyse the approval trends over a ten-year time horizon. METHODS: All ODs authorised by the European Medicines Agency (EMA) and approved by the US Food and Drug Administration (FDA) were identified on the 1^st May 2015 by downloading the databases available from their respective websites. Duplicates were removed in both cases using non-proprietary name and the lists were filtered to capture the period from 01/01/2005 to 31/12/2014. RESULTS: The databases downloaded from the EMA and FDA had n=93 and n=237 results respectively. Removing the duplicates reduced these to n=91 and n=197 respectively. Filtering the list to select ODs authorised between the 01/01/2005 and 31/12/2014 gave final values of n=74 and n=189 respectively. ANALYSIS: The number of ODs approved significantly increased in numbers between the years 2005 and 2014 in the US and in the EU. In 2014 the EMA authorised 5 times as many ODs as they did in 2005 (15 vs 3 respectively) and a similar trend was observed in the US, where in 2014 the FDA authorised twice as many ODs as they did in 2005 (30 vs 14). CONCLUSIONS: In 2005 the number of ODs authorised was significantly lower than that of 2014 and the designation of orphan diseases and approval of ODs was rare. 10 years on and gaining OD status for a sub population based rare disease appears from the outside to have become an objective for a number of pharmaceutical companies.