The period 1990-1997 saw the implementation of a nationwide breast cancer screening programme in the Netherlands, which provided biennial mammography for all women aged 50-69 years (50-75 years at present). The National Evaluation Team monitors the programme annually collecting regional data on screening outcomes; regional cancer registries provide data on interval cancers and on breast cancers in unscreened women by linkage of cancer registry data to data on screened women. Of 4 million women invited, 78.5% attended for screening. Screening resulted in 13.1 referrals, 9.2 biopsies and 6.1 breast cancers detected per 1000 women screened initially (6.9, 4.5 and 3.5 per 1000 in subsequently screened women, respectively). Within the first 2 years following screening 0.95 interval cancers per 1000 women-years were diagnosed. The stage distribution of screen-detected cancers was more favourable than that of interval cancers and of those diagnosed in unscreened women. The results are largely consistent with expectations. Results may nonetheless be further improved, particularly the detection rate in subsequent screens.