The GPRD is a computerized database of anonymized data from patient records. Data have been collected continuously since 1987. Currently, information on approximately 3.6 million patients in the UK, equivalent to about 6% of the population, are collected from over 480 general practices nationwide. Who runs the GPRD? The database is run, on a non-profit making basis, by the UK Medicines and Healthcare products Regulatory Agency (MHRA) in London. The MHRA is an Executive Agency of the Department of Health. It fulfills a critical public health role in the UK by ensuring that all medicines and medical products meet appropriate standards of safety, quality, and efficacy. The MHRA has a long history of handling patient data responsibly, in the course of monitoring the safety of UK medicines. Guidance from the General Medical Council strongly encourages doctors to ‘co-operate by providing relevant information wherever possible’ to bodies such as the MHRA.