PURPOSE: To determine whether radiofrequency thermal ablation can be used to treat benign cystic lesions in a porcine gallbladder model. MATERIALS AND METHODS: This experimental study of radiofrequency thermal ablation involved the use of 15 exvivo porcine gallbladders and 15-G expandable needle electrodes. To investigate optimal temperature parame-ters,three groups of five were designated according to target temperature: Group A: 70 degrees C; Group B: 80 degrees C; Group C: 90 degrees C. After the target temperature was reached, ablation lasted for one minute. Gallbladder width, height and length were measured before and after ablation, and the estimated volume reduction ratios of the three groups were compared. Whether adjacent liver parenchyma around the gallbladder fossa was ablated by heat conducted from hot bile was also determined, and the thickness of the ablated area of the liver was measured. RESULTS: The volume reduction ratio in Group A, B and C was 42.7%, 41.7% and 42.9%, respectively (p>.05). In all 15 cases, gallbladder walls lost their transparency and elasticity at about 70 degrees C. In nine of ten cases in Groups B and C, the hepatic capsule around the gallbladder fossa was retracted at about 80 degrees C. The mean thickness of liver parenchymal damage adjacent to the gallbladder was 5.4 mm in Group B and 9.8 mm in Group C. In Group A livers, only one case showed minimal gradual parenchymal change. Microscopically, all three groups showed complete coagulation necrosis of the wall. CONCLUSION: On the basis of this feasibility study, radiofrequency thermal ablation is potentially suitable for the ultrasound-guided treatment of symptomatic cystic lesions including benign hepatic or renal cyst.