A clinical and galactographic investigation was carried out on 103 patients with hematic, serous-hematic, and serous nipple discharge. The age of the patients ranged from 18 to 72 years. A single papilloma was found in 20 cases, diffuse papillomatosis in 2 cases, atypical ductal hyperplasia in 8 cases, and ductal carcinoma in 4 cases (3 of these were infiltrating and 1 was noninfiltrating associated with a diffuse papillomatosis). Mammography gave no indications of carcinoma in any of the 4 cases. In the remaining 49 patients, pictures of ductal hyperplasia, periductal mastitis or sclerosis, sclerosing adenosis, or ductal ectasia were observed. The various types of lesions were often associated. Lacunae, stenosis, or occlusion of the ducts, evidenced by galactography, correlated well with the histologic findings of proliferative lesions of the ductal epithelium. Nevertheless, in practice, it should be the type of discharge that indicates surgery rather than galactographic or cytologic data, which appeared to have little diagnostic value. The frequency with which preneoplastic (or limit) lesions, and also nonsuspect carcinomas were found in patients with a significant nipple discharge confirm the importance of this symptom for a secondary prevention of early diagnosis of mammary neoplastic lesions originating from galactophorous ducts. Finally, complete resection of the galactophorous ducts must be considered as the best treatment in all patients with a suspicious nipple discharge that requires surgery.