Contrast medium was injected percutaneously into palpable breast lesions in 63 patients in order to demonstrate lactiferous ducts. Of 35 benign and mammographically definable tumours, 30 were successfully punctured and ducts were visualized in 20, while ducts were demonstrated in seven of 21 non-definable lesions. Ducts were seen in 10 of 13 fibroadenomas removed by surgery, in two of four hamartomas, and in two of three cases of mastitis. No ducts were seen in six solid, malignant tumours examined, while one intracystic papillary carcinoma showed filling defects caused by the malignant growth. It was concluded that the method is simple, and that the demonstration of ducts is an indication of the benign nature of a lesion.