A national program for systematic breast cancer screening, aimed at reducing breast cancer mortality, was established by the Directorate General for Health in 1994. This program is based on the recommendations of the European Cancer Program. In accordance with national guidelines, each of the 32 departments conducting organized breast cancer screening as part of the national program sends standardized aggregated data once a year to the InVS. The performance of early indicators of the program’s impact, quality, and effectiveness is analyzed at the departmental and national levels. As of December 31, 1998, the evaluation confirms an increase in participation rates in most departments compared to the previous year. The early indicators of the program’s effectiveness are in line with European recommendations. A high rate of small-sized cancers and cancers without lymph node involvement was detected through the systematic invitation to the first mammogram. The results for subsequent mammograms show an increase in the detection of these cancers with a better prognosis. Detailed indicators on the quality, impact, and effectiveness of the screening program allow for an accurate assessment of the situation and an evaluation of the benefits of an organized program, as well as an assessment of its adverse effects and their trends over time (reduction in the number of false positives, improvement in the positive predictive value of surgical biopsies, etc.). Data on screening practices among women undergoing their first mammogram under the program show that the program targets women who do not undergo mammograms or do so irregularly: 28% of women had never had a mammogram, and 33% had had a mammogram more than three years prior. (R.A.)