Sixty-two cases of invasive breast cancer were identified in a large cohort of women previously treated for biopsy-proven benign breast disease (BBD) at the Breast Unit of CSPO, in Florence, along with a group of 315 controls, strictly matched by age and year of diagnosis. A pathologist reviewed and reclassified all the original BBD slides according to recently proposed criteria (no evidence of epithelial proliferation, epithelial proliferation without or with atypia). Information about potential confounding factors was collected during personal interviews. In comparison to the women with "non-proliferative" BBD, women classified as having "proliferative disease without atypia" showed a weak and non-significant increase in risk (OR 1.3; 95% CI: 0.5-3.5). In contrast, women with "atypical hyperplasia" were at very high risk of developing breast cancer (OR 13.0; 95% CI: 4.1-41.7). When planning mammography screening or other large-scale early-diagnosis programmes for breast cancer in the general female population, follow-up of high-risk subgroups of BBD patients should be considered.