Fine-needle aspiration cytology has been already established as a reliable method for the diagnosis of breast cancer. Its application has been recently extended to immunocytochemical analysis of biological parameters. In the current study estrogen and progesterone receptors, Ki67 growth fraction, and p53 protein expression were immunocytochemically evaluated on the cellular material sampled by the same fine-needle aspirate used for the conventional cytologic diagnosis of malignancy. Fine-needle aspiration specimens from 100 patients with primary breast carcinoma were submitted to the immunocytochemical analysis. Twenty-eight percent were in premenopause; 23% had tumors with a diameter less than 2 cm, 59% from 2 to 5 cm, and 18% more than 5 cm; 60% had axillary nodal status negative, 34% positive, and 6% unknown. The concomitant immunocytochemical evaluation of all parameters was possible in 70% of the patients. A significant association was found between p53 overexpression and Ki67 values (p = 0.004), and between Ki67 values and progesterone receptor status (p = 0.003). No correlation was found between any parameter and clinical tumor size. Estrogen (p = 0.02) and progesterone (p = 0.04) receptor negativity and high Ki67 growth fraction (p = 0.005) were significantly associated with the clinical evidence of axillary node involvement. This study suggests that fine-needle aspiration cytology represents an effective practice for a simultaneous evaluation of multiple biologic indicators and could be useful as a preoperative procedure in patients who are candidates for neoadjuvant chemotherapy and/or endocrine therapy.