A “gray zone“ exist in fine needle aspiration cytology of breast; there an unequivocal diagnosis can not be made. Previous studies have reported an “atypical and suspicious” cytologic category incidence of 2-19%, which is also defined as “gray zone”. We reviewed 1019 fine needle aspirations of the breast performed at our institution to determine the incidence of the “true gray zone” and establish guidelines to minimize the size of the gray zone. 107 cases (10,5%) were initially interpreted as suspicious category. The cytologic smears from all 107 equivocal cases and histopathologic sections from 60 of these patients who underwent a biopsy or mastectomy were reviewed. The causes of the equivocal diagnoses were divided into three categories: (1) technical problems (limited cellularity or poorly preserved specimens); (2) inexperience, which included cases that were reclassified by the reviewing cytopathologist as benign or malignant; (3) the overlap of cytologic features of benign and malignant lesions due to the nature of the lesion; justifying a confirmational biopsy. Excluding the first two factors resulted in a true gray zone of approximately 4,5%. The majority of cases in the true gray zone were confirmed as well differantiated low grade carcinoma.