From Jan. 1, 1990 to Dec. 30, 1994, 38 patients with mammary duct ectasia admited to our hospital, for whom the diagnoses were confirmed by pathological examination of surgical specimens. Intensive literature review was made together with 569 cases of this group were summarized in terms of clinical features of the disease. Tumor-like mass is a most common sign (78.21%), and the other clinical features are: nipple discharge (28.47%), nipple retraction (21.79%), axillary node enlargement (15.82%), skin adhesion (11.25%) and breast fistula (3.87%). Surgical excision of the mass is the unique effective treatment of chioce. 24 out of 38 cases were misdiagnosed other than mammary duct ectasia. Careful clinical observation and examination may reduce the chance of misdiagnosis.