The OECD REGPAT database presents patent data that have been linked to regions according to the addresses of the applicants and inventors. The data have been 'regionalised' at a very detailed level so that more than 2 000 regions are covered across OECD countries. REGPAT allows patent data to be used in connection with other regional data such as GDP or labour force statistics, and other patent-based information such as citations, technical fields and patent holder's characteristics (industry, university, etc.), thus providing researchers with the means to develop a rich set of new indicators and undertake a broad range of analyses to address issues relating to the regional dimension of innovation. By making regionalised patent data available to all students interested in the field, the OECD aims to stimulate research and contribute to a better understanding of the regional dimension of innovation. In addition, the methodology used for the construction of REGPAT is published, to give users the opportunity to suggest modifications and thus contribute to improvements in the quality of REGPAT. The full technical description of the REGPAT database as accessible to users is provided in annex. Patent data provide unique insights into the outcome and characteristics of inventive activities, including at regional level. They have limitations however, like all data sources, and should be handled with methodological care.