Estimating the economic burden of specific diseases by means of cost of illness studies is frequently carried out in European countries and the United States. In Ireland however, there continues to be a lack of such costing data for the various diseases. This can be problematic for estimating budgets within the healthcare system and also for proving the cost effectiveness of the new and expensive medications that impact significantly on the Irish drug market. The aim of cost of illness studies is to identify and measure all the costs of a particular disease including the direct, indirect, and intangible aspects. They are not economic evaluations as alternatives are not compared but they can help to determine research and funding priorities by emphasising where inefficiencies are present and where savings can be made as they identify the different components of cost and therefore areas of high expenditure.