Fine-needle aspiration biopsy (FNAB) is considered a valid diagnostic procedure in management of patients with breast lesions. It is also important to differentiate benign nonproliferative change from proliferative breast changes, since the risk of development of breast carcinoma in patients with atypical hyperplasia is 4-5 times that of general population. Therefore, the recognition of proliferative breast disease with atypia significantly impacts on the patient's subsequent management. To assess the feasibility of a cytologic grading system to further characterize benign breast lesions, cytologic preparation of 87 mammographically guided FNABs were studied. Cellular aspirates were evaluated for the cellular arrangement, the degree of cellular pleomorphism and anisonucleosis, presence of myoepithelial cells and nucleoli and the status of the chromatin pattern. Values ranging from 1 to 4 were assigned to each cytologic criterion, and a score based on the sum of the individual values was calculated for each case. The minimum score attainable was thus 6. In our chosen criteria cytologic diagnosis of nonproliferative disease was entertained when the total score ranged from 6 to 10. Proliferative disease without atypia was diagnosed with a total score ranging from 11 to 14. Atypical hyperplasia was reported when the total score ranged from 15 to 18. A cytologic diagnosis of malignancy was entertained when the total score ranged from 19 to 24. The cytologic diagnosis was then compared to the reported histologic diagnosis from the excisional biopsies and the data were statistically analysed. A high degree of concordance was found between the cytologic findings and the histologic diagnosis. This study suggests that it is possible to apply a cytologic grading system to further subclassify benign breast disease and distinguish these forms from neoplastic lesions.