In mammographically detected breast lesions, only 10% to 25% of biopsy specimens are malignant. Furthermore, the current method of needle localization of these lesions is cumbersome and inefficient. Stereotaxic needle aspiration was used to examine 84 patients. Successful localization with the needle tip within 1 to 2 mm of the suspected lesion was possible in 80 cases (95.2%). Following aspirate cytology, the lesion was localized with indigo carmine and Kopans' wire and every patient underwent a standard open excisional biopsy. Twelve cases of breast cancer were diagnosed histologically. Eleven of these cases were correctly diagnosed cytologically, while one case yielded a false-negative result. In the remaining 72 histologically benign cases, four lesions were reported cytologically to be atypical. There were no complications. Stereotaxic needle aspiration localizes occult breast lesions precisely and in conjunction with mammography, and it is an acceptable preoperative method of diagnosing nonpalpable breast tumors.