BACKGROUND: Mammography screening is a promising method for improving prognosis in breast cancer. PATIENTS AND METHODS: In this economic analysis, data from the Norwegian Mammography Project (NMP), the National Health Administration (NMA) and the Norwegian Medical Association (NMA) were employed in a model for cost-effectiveness analysis. According to the annual report of the NMP for 1996, 60,147 women aged 50-69 years had been invited to a two-yearly mammographic screening programme 46,329 (77%) had been screened and 337 (0.7%) breast cancers had been revealed. The use of breast conserving surgery (BCS) was in this study estimated raised by 17% due to screening, the breast cancer mortality decreased by 30% and the number of life years saved per prevented breast cancer death was calculated 15 years. RESULTS: The cost per woman screened was calculated 75.4 Pounds, the cost per cancer detected 10.365 Pounds and the cost per life year (LY) saved 8.561 Pounds. A raised frequency of BCS, diagnosis and adjuvant chemotherapy brought two years forward, follow-up costs and costs/savings due to prevented breast cancer deaths were all included in the analysis. A sensitivity analysis documented mammography screening cost-effective in Norway when four to nine years are gained per prevented breast cancer death. CONCLUSION: Mammography screening in Norway looks cost-effective. Time has come to encourage national screening programmes.