During a 34-month period 2050 fine needle aspiration biopsies of solid or cystic palpable breast lesions were performed. Of the 1182 patients with solid lesions, 384 underwent 405 surgical procedures. Carcinoma was the histologic diagnosis of 118 lesions. Of these, aspiration cytology had identified 92 (78%) as malignant; in 13 (11%) a malignant condition was suspected; 9 (7.6%) had been falsely assessed as benign. Cytology reports were accurate in 237 (83%) of the 287 histologically confirmed benign lesions. There were no false-positive reports. The 243 patients with cystic lesions underwent 572 aspirations for diagnosis and as treatment. Four lesions were excised and found to be benign. Needle aspiration biopsy is a most valuable tool. It is safe, simple, quick, repeatable and easily accepted by patients. Its positive predictive value is excellent (100% in our series). Cytology reports negative for malignant change should be disregarded if cancer is suspected clinically.