To analyze the sensitivity, specificity, positive and negative predictive values and the efficacy of fine needle aspiration (FNA) in our material, to investigate the influence of the histologic type and stage of carcinoma on the quality of the aspirates and on the detection rates of mammary carcinoma, and to investigate the rate of inadequate samples and the accuracy of cytologic diagnoses, with an emphasis on the rate of false positive diagnoses in benign mammary lesions. The results of 1,472 FNAs of the breast obtained over three years were subjected to a retrospective analysis. The cytologic diagnoses were benign in 1,003 cases (68.1%), suspicious in 49 (3.3%) and malignant in 181 (12.3%); 239 (16.2%) of the aspirates were inadequate. In 393 (26.6%) of the cases and in 85% of cytologically malignant smears, the aspirate was compared with histologic examination. The rate of false negative FNAs was 9.0%. The proportion of inadequate cases was clearly related to stage (pT): it was 9.5% in pT1, 5.0% in pT2 and 0% in pT3. Among invasive carcinomas the sensitivity was 89.9%, specificity 99.3% and overall accuracy 88.5%. Among the cases diagnosed cytologically as benign, 182 were compared with biopsies. Of these, 79.9% were true negative, 0.5% (1 case) was false positive, and 15.4% had insufficient cells for evaluation. FNA cytology has improved decision making and the selection of patients for biopsy of mammary lesions and has contributed to saving time in the clinical management of breast lumps. In no case did FNA lead to inadequate clinical measures or other disadvantages to patients. Thus, FNA cytology is an indispensible diagnostic tool in the management of breast lesions.