The REP is a population-based medical records-linkage system designed to support epidemiologic and health services research by enabling comprehensive follow-up of individuals across multiple healthcare providers. As of 2018, the REP includes over 690,000 participants from a 27-county region in southern Minnesota and western Wisconsin, expanding from its original base in Olmsted County in the United States of America. Recruitment began in 1966 in Olmsted County, where individuals were enrolled through their routine visits to local healthcare providers. The project was expanded in 2010 to include additional counties, adding over 540,000 new participants. This was motivated by the need to study rare conditions and underrepresented populations. Participants are followed up continuously through their routine healthcare data, with data updated annually from participating institutions.

Recruitment is ongoing