It is widely known how the early diagnosis and treatment of breast cancer may lead to better prognosis. When a non-palpable breast lesion detected with mammography is correctly localized with fine-needle biopsy under X-ray guidance, the surgeon can easily remove the lesion while preserving normal breast tissue. In such cases, histology is also possible. The authors describe an easy bidimensional technique for the preoperative localization of occult nonpalpable breast lesions with a fine-needle. The procedure is feasible also with out-of-date equipment and does not cause any discomfort to the patients. It should be performed on all women with mammographic suspicion of non-palpable breast lesion. From January through December 1989 the authors performed 64 preoperative fine-needle biopsies of clinically-occult breast lesions. The presence of a lesion associated with microcalcifications was found to be indicative of malignancy more often than in the case of microcalcifications or lesions alone. Of 64 cases, histology demonstrated malignancy in 31 patients.