In 1975 the first programme in the Netherlands for population screening on breast cancer by mammography was started in Nijmegen. The positive results of this and other studies have led to a national screening programme. To ensure a good result, a centralised approach was chosen for the quality assurance (QA) in the radiology, the pathology and the physics of mammography. The National Expert and Training Centre for Breast Cancer Screening was set up as a Reference Centre for mammography. For the physics part, a protocol for acceptance testing, routine inspection and daily quality control (QC) was produced in close cooperation with leading manufacturers of film-screen combinations and X ray equipment. The protocol is used by the Reference Centre to evaluate the equipment before the start of a screening centre in the national project is allowed. Part of this protocol is used for the daily QC. The digitised data on the quality of X ray equipment and film processing of every unit are sent to the Reference Centre for evaluation every day, by telephone and modem. The protocol is accepted by the Ministry of Health, and it has been adopted as a directive for every screening unit by the National Health Insurance Council.