Background: Health disparities between adults with intellectual disabilities (ID) and the general population have been well documented but, to date, no dedicated assessment battery for measuring health disparity has been available. This paper reports on the development and testing of a multinational assessment battery for collecting data on a range of health indicators relevant to adults with ID. Methods: An assessment battery (the P15) was developed following piloting, and administered to samples of adults with ID, in 14 EU countries. Samples were neither random, nor representative of the countries from which they were drawn. However, within the local health administration areas selected in each country, efforts were made to ensure samples were broadly representative of the typical living circumstances, ages and ability levels of the administrative population of adults with ID. The total sample comprised 1269 adults with ID, of whom 49% were female. The mean age was 41 years (range 19 to 90). Results: Overall, feasibility, internal consistency and face validity of the P15 was acceptable. Conclusions: With some refinement the P15 could be useful for collecting data on health indicators known to be particularly important for adults with ID. It is useable in a range of countries and has the potential to highlight health inequity for adults with ID at a national or local level. Larger scale epidemiological studies are needed to exploit the potential of the P15 to address health inequity in this group.