In 1992, a national screening mammography program, including female patients between 50 and 64 years of age, was launched in Luxembourg. The effects of this campaign on the different diagnostic procedures, especially fine needle aspirations (FNA), large core needle biopsies (LCNB), and surgical specimens, were analyzed. From 1983 to 1997, the National Cancer Registry recorded 3167 new cases of invasive female breast cancer, all histologically diagnosed in one central pathology department. In 1996, the population consisted of 418,300 inhabitants (212,900 females). The number of breast cancer, tumor size, the nature of the diagnostic procedures, their diagnostic value as well as the number of physicians, "aspirators", and "biopsists" were evaluated. Between 1992 and 1994, the incidence of invasive breast cancers increased, concomitant with the launching of a National Screening Mammography Program. The diagnosis of in situ cancers tripled, and the mean size of invasive breast cancer decreased from 2.1-2.4 cm to 1.1-1.4 cm. Since 1994, the number of FNA had remained stable, LCNB had increased by 417.5%, and surgical biopsies had decreased by 18.95%. Between 1995 and 1997, 28.37% of 1075 FNA, and only 9.6% of 465 LCNB yielded inadequate samples. FNA were done by 77 different doctors (53.25% being gynecologists) and LCNB by 34 (52.94% being radiologists). The first diagnoses of all invasive cancers (n = 790) were made by using frozen sections from surgical specimens in 58.35% (n = 461), LCNB in 18.23% (n = 144), mastectomy in 10.13% (n = 80), formalin-fixed biopsies in 9.49% (n = 75), and FNA in 3.17% (n = 25). There are beneficial effects (increase in the number of diagnoses of in situ cancer; decrease in tumor sizes) not only for the "target" age group (50-64 years), but also for all female age groups (> 15 years). For quality assurance purposes, it is absolutely recommended to carry out pathological, radiological, and diagnostic work in specialized centers.