Breast cancer screening is generally accepted as an effective means of reducing breast cancer mortality in post-menopausal women. In this analysis the impact of nationwide screening on clinical medicine and the effects for the women involved are quantified. Effect estimates are based on results from screening trials in Utrecht (DOM-project) and Nijmegen, and on bi-annual screening of women aged 50-70. The consequences for health care are based on generally accepted assessment and treatment policies. The number of assessment procedures for non-palpable lesions will increase by 12% per year in the build-up period, and will remain slightly higher. The total number of biopsies in a real population is expected to decrease. Screening will lead to a shift in primary treatment modalities, as 15% of mastectomies will be replaced by breast conserving therapy. The temporary increase in the demand for primary treatment in the first years will be followed by a decrease in the demand for treating women with advanced disease. Favourable effects outweigh the inevitable unfavourable effects, with high quality screening and an appropriate invitation system. Breast cancer screening can also be recommended after considering other consequences than mortality reduction.