There is evidence that patient choice and the quality of service delivery in primary care can be influenced by the organisation and structure of provision at the local level. However, the formal measurement of structure in primary care has yet to be undertaken. Using data for Coventry, standard concentration measures are estimated, which show that concentration varies considerably across the city and tends to be higher in areas of lower deprivation. Assuming that patient choice is an important consideration in health care planning, concentration measurement may provide a useful tool for health authorities in making decisions about GP numbers, practice mergers and re-location.