Elastosis, an abundance of elastic tissue, is commonly present in breast carcinoma. However, its diagnostic significance remaines an unsettled issue. This study documents 17 cases of elastosis occurring in a distinctive benign sclerosing ductal lesion of the female breast (Fenoglio and Lattes: Cancer 33: 691-700, 1974). Elastosis was characterized by staining reactions and, in several instances, by elastase digestion and electron microscopy. Yellow streaks and flecks may be apparent grossly and probably reflect the increased elastic tissue. Histologically, the lesion is generally stellate with central sclerosis and marked peripheral intraductal and ductular hyperplasia which is often papillary. Elastosis, which may be marked, is a constant finding and is predominantly periductal in location. It is emphasized that the gross and histologic features of the lesion may mimic carcinoma and that elastosis may be found in benign ductal lesions of the breast.