Reduction mammoplasty is a frequently performed procedure for the treatment of macromastia and for the achievement of symmetry in breast cancer patients following lumpectomy. Slides from 516 consecutive bilateral reduction mammoplasties performed for macromastia over 15 years were reviewed. Among these, 92 (18%) low-risk ductal intraepithelial neoplasia/intraductal hyperplasia, 28 (5%) ductal intraepithelial neoplasia 1 (1 low-grade ductal carcinoma in situ, 11 atypical intraductal hyperplasia, and 16 flat type), 17 (3%) lobular intraepithelial neoplasia, and 1 (0.2%) tubular carcinoma were identified. The patients were categorized into 3 age groups: <40 (n=352), 40 to 50 (n=107), and over 50 years (n=57); the frequency of the lesions increased with age. These data confirm the low frequency of clinically occult malignancies identified in reduction mammoplasty specimens and provide substantial information about the frequency of a variety of intraepithelial proliferations. Preoperative mammography, specimen orientation, and inking of margins with 1 color are advised when reduction mammoplasty is scheduled for women>or=40 years of age.