A cytologic grading method of fine needle aspiration smears has been applied to 192 cases of breast carcinoma. Grade I defines well differenciated carcinoma, grade II pleioporphic tumor cells, grade III anaplastic carcinoma. Special attention was given to the unfavorable forms of tumors (grade III). The cytologic grading was correlated with the NMT clinical classification, with the notion of acute exacerbation and with axillary nodes involvement. The correlation of grading with the clinical course of the disease was evaluated after a twelve months follow up. In 4% of patients classified in grade I, 8% of grade II and 58% of grade III, metastases, local recurrence or death had occurred within one year. The contribution of grading to the identification of fast growing tumors is discussed.