Seventeen cases of fibrous tumor of the breast are reported in persons between 23 and 55 years of age, 16 women and one man. Mammography was not diagnostic. It is a localized proliferation of the interlobular and perilobular connective tissue with hypoplasia of the mammary ducts and lobules. It is the rarest of the benign tumors of the breast. Local excision was done in all cases and no recurrences have been observed. In one breast, a fibrous tumor was found at another area at a later date.