Reduction mammaplasty (RM) is a common surgical procedure that yields a variable amount of tissue for pathologic examination. Occult breast carcinomas are detected rarely in these specimens. We evaluated the pathologic findings in RM specimens performed in our institution during an 11.5-year period (July 1989 to December 2000). A total of 560 patients who had undergone RM were identified, 503 bilateral and 57 unilateral. The average number of blocks submitted per breast was 3.9 (range, 1–23). Pathologic changes were present in 338 cases (60.4%). Unsuspected carcinomas (small invasive carcinomas, 3; ductal carcinoma in situ, 1) were found in 4 cases (0.7%). Atypical ductal and/or atypical lobular hyperplasia were identified in 8 cases (1.4%). Lesions associated with a mildly increased carcinoma risk (moderate/florid ductal hyperplasia, sclerosing adenosis, and papilloma) were identified in 52 cases (9.3%). Other findings included fibrocystic changes, fibrosis, mild ductal hyperplasia, fibroadenoma, and adenosis. Pathologic examination of RM specimens provides important clinical information and should be performed routinely.