Clinical Practice Research Datalink (CPRD) is a real-world research service supporting retrospective and prospective public health and clinical studies. CPRD is jointly sponsored by the Medicines and Healthcare products Regulatory Agency and the National Institute for Health Research (NIHR), as part of the Department of Health and Social Care. CPRD collects de-identified patient data from a network of GP practices across the UK. Primary care data are linked to a range of other health-related data to provide a longitudinal, representative UK population health dataset. The data encompass 50 million patients, including 14 million currently registered patients.