Objective To evaluate the safety and efficacy of ultrasound-guided percutaneous microwave ablation of renal neoplasms.Methods Twenty-two patients with pathologically proven renal neoplasms(18 renal cell carcinoma,3 renal angiomyolipoma,1 oncocytoma)with diameters of 1.0 to 3.8 cm were treated by microwave ablation.Cooled-shaft needle antenna was percutaneously inserted into the tumors under ultrasound guidance.One antenna was used for tumors less than 2 cm,two antennas were used for tumors larger than 2 cm.One thermal couple was placed adjacent to the tumor monitoring temperature in real-time during ablation.Immediate treatment efficacy was assessed by contrast-enhanced ultrasound within 3 days after ablation.Short-term efficacy was assessed by contrast-enhanced CT and/or contrast-enhanced ultrasound at 1,3,6 months and every 6 months thereafter.Results Twenty tumors were completely ablated in a single session,2 tumors were completely ablated in 2 sessions.No complications occurred.No residual tumor or recurrence was observed during follow-up.Conclusions Ultrasound-guided pereutaneous microwave ablation appears to be a safe and effective technique for the management of renal neoplasms in selected patients.