The objective of this study was to assess the diagnostic value of preoperative cytology and galactography in women with nipple discharge using a simple intraductal aspiration method. From May 1997 to February 2002, 172 patients with unilateral, spontaneous nipple discharge without palpable masses underwent intraductal aspiration cytology followed by galactography. Major duct excision was performed in 133 of 155 successful cases. Pathological findings showed solitary papilloma in 65 cases, breast cancer in 16 cases, fibrocystic disease in 17 cases, papillomatosis in 12 cases, ductal hyperplasia in 11 cases, and finally, duct ectasia in 12 cases. Our results showed sensitivity of 75.0% and 68.8%, specificity of 86.3% and 62.4%, and overall accuracy of 85.1% and 63.2%, respectively, for cytological analysis and galactography. This suggests that the intraductal aspiration method for preoperative cytology and galactography is a minimally invasive and well-tolerated procedure that seems to be useful in differentiating between benign and malignant lesions in patients with unilateral, spontaneous nipple discharge.