The aim of this study was to test the efficacy of four different radio-frequency ablation (RFA) systems in normal hepatic parenchyma in large animals. The RFA was applied to pig livers in vivo and to calf livers ex vivo using the Radionics cluster needle, RITA starburst XL needle, Radiotherapeutics Le Veen 4.0 needle, and the Berchtold 14-G saline-perfused 15-mm active-tip needle based on constructor specifications. The volume of tissue coagulation from RF was calculated from measurements of the vertical diameter (Dv) and transverse diameter (Dt). Lesion shape was characterized using the ratio between Dt/Dv. Radiotherapeutics and RITA produced in vivo lesion volume of 42+/-10, 39+/-4 cm3 with a reproducible spherical shape (Dt/Dv of 1.01+/-0.16 and 0.97+/-0.1, respectively). Radionics produced in vivo RF lesions volume of 29+/-11 cm3) with an ovoid shape (Dt/Dv 0.88+/-0.09). The RF lesions with the Berchtold device could not be assessed in vivo as 5 of 8 animals died during treatment. Ex vivo RF lesions had similar volumes with each system; however, the Radiotherapeutics device produced more reproducible shaped lesions than the other systems. In our experimental study, we found no difference between expandable needle systems in vivo. Cooled needles produced slightly smaller and ovoid shape in vivo lesions.