A cost-effectiveness analysis has been conducted in order to evaluate effects and costs of a nationwide mammographic breast cancer screening programme compared with no screening in a 30 years period. The analysis includes seven different phases of breast cancer, from the screening programme itself to the treatment of terminal illness. The estimates use italian published data and field studies. The calculations were performed with the Miscan computer simulation package: a programme providing for the screening of women aged 50-69 at two years intervals might be expected to result in a 1,650 deaths prevented and 14,500 years of life gained each year. The overall net costs of the programme were assessed at between 2,893 and 3,212 thousand million lire, the cost per life saved between 59.8 and 66.4 million lire and the cost per life-year gained between 6.6 and 7.3 million lire (between 10.7 and 11.5 million lire with a 5% discount rate, an estimate lower than that of German programme). The analysis produces important information for the Italian policy debate over mammography and it also contributes to the development of economic evaluation in our country.