Proliferative breast diseases include a group of lesions which occupy an intermediate position between benign and malignant lesions and are extremely likely to develop into carcinomas. The authors studied 81 patients who had been surgically biopsied on the basis of mammographic and/or US findings. In 33/81 (40.7%) of them proliferative lesions were diagnosed at histology. Mammography was able to identify 18/33 lesions (54.5%) versus US 26/33 (81.8%). On the basis of these findings, a group of patients at risk for cancer could be identified. As a matter of fact, proliferative lesions, especially those presenting with atypical hyperplasia, are associated with a higher risk of developing into carcinomas than those presenting with typical features. For these patients, the authors suggest more frequent clinical and instrumental screening.