Real-time ultrasound-guided fine-needle aspiration biopsy in 137 solid breast masses was performed. Sonographic findings were categorized into three group and aspirates were categorized into three cytologic groups. The cytologic result was reported benign masses (cytologic group 1) in 71 cases (52%), malignant masses (cytologic group 2 and 3) in 44 cases (32%) and insufficient specimens in 22 cases (16%). Insufficient specimens were treated as benign masses. Excisional biopsy in 44 malignant masses and 3 benigh masses according to cytologic results, clinical findings and follow up study was performed. The result was reported 41 malignant masses and 6 benign masses. Based on cytologic criteria, sensitivity for detection of malignancy was 93% and specificity was 94%. In conclusion, the high specificity provided by ultrasound-guided fine-needle aspiration biopsy could markedly reduce unnecessary surgical excisions for benign masses and it should be routinely performed, since it can give physical and emotional benefits to patients and lead to earlier and cost effective diagnosis of breast cancer.