A total of 219 fine needle aspiration (FNA) biopsies of the breast were performed during the period 1983 to 1985 at a tertiary medical center. The series consisted of 215 women (98.2%) and 4 men (1.8%), with an are range of 14 to 90 years (mean of 46.5 years). Histologic confirmation (93 cases) or clinical follow-up for up to two years was obtained. The sensitivity of the FNA procedure was 82.2%, its specificity was 98.8%, and the overall efficiency of the test was 95.4%. The false-negative rate was 4.4%, with no false-positive diagnoses for the primary diagnosis of breast carcinoma. We have found that one of the major advantages of FNA biopsy is that it lowers costs by allowing the surgeon to triage which patients should have an outpatient excisional biopsy under local anesthesia and which patients should have a one-stage inpatient procedure with frozen section confirmation. For this triage role, suspicious diagnoses (3.2%) were included in the positive group and atypical (1.8%) and insufficient diagnoses (6.8%) in the negative group. Taking into account the FNA biopsy cost of $75, the procedure resulted in a savings per case of $262 over the cost that would have occurred if all cases had had routine inpatient biopsy and $154 per case over the cost that would have occurred with routine outpatient biopsy of all cases. Our results indicate that FNA breast biopsy is a diagnostically accurate and economical triage procedure, even when followed by an excisional or frozen-section biopsy for confirmation. The use of FNA biopsy could be expanded to a greater number of medical centers and decrease the potential for false-positive diagnoses by combining FNA biopsy with frozen-section confirmation.