A diagnostic test study was conducted to evaluate the effectiveness of ultrasoundguided fine needle aspiration cytology - at Hung Vuong Hospital - in the diagnosis of solid breast tumors. Results: Among 201 enrolled women, malignancy was diagnosed in 38 cases (18.9 percent) on fine needle aspiration cytology (FNAC), most of which were duct carcinomas. The sensitivity, specificity, poSitive predictive value, negative predictive value and falsenegativity of FNAC in the present study were 97.36 percent, 100 percent, 100 percent, 99.39 percent, and 0.61 percent, respectively. Complications of the procedure were minimal. Conclusion: Ultrasound-guided FNAC is a safe, cheap, reliable and less traumatic diagnostic tool with high efficiency.