In several studies it has been shown that breast cancer screening by means of mammography reduces breast cancer mortality. To ensure that when organising a service screening programme the aim is reached, it is necessary to control and monitor the process. This is possible by several methods. In this study, disease-free intervals and survival rates were used as monitoring tools. The DOM project, a breast cancer screening programme for women aged 50-64 years old at intake, started at the end of 1974. All breast cancer cases diagnosed between 1973 and 1989 were followed up to 1991. It is clear that disease-free interval and survival rates are proper predictors of the effects of screening on breast cancer mortality.