STUDY OBJECTIVE In 1998, the International Breast Cancer Screening Network (IBSN) sponsored an assessment of quality assurance policies and practices to define their scope for population-based screening mammography programmes across IBSN countries. DESIGN Analysis of data from a survey designed to assess multiple elements of screening programme quality assurance, including organisation of quality assurance activities, mechanisms for site visits and accreditation, requirements for quality control and data systems, and inclusion of treatment, follow up, and programme evaluation in screening mammography quality assurance activities. PARTICIPANTS AND SETTING IBSN representatives in 23 countries completed a comprehensive questionnaire between May and December 1998. MAIN RESULTS Completed questionnaires were obtained from all 23 countries. Responses indicated that countries vary in their approaches to implementing quality assurance, although all monitor components of structure, process, and outcome. Nearly all have in place laws, surveillance mechanisms, or standards for quality assurance. In all countries, quality assurance activities extend beyond the screening mammography examination. CONCLUSIONS The assessment has enhanced understanding of the organisation of screening mammography programmes across countries, as well as the comparability of screening mammography data. All countries have established mechanisms for assuring the quality of screening mammography in population-based programmes, although these mechanisms vary across countries.