Purpose: To investigate the effect of change in portal vein flow rates on the size and shape of ablations created by a bipolar radiofrequency (RF) ablation device. Materials and Methods: This study was exempt from institutional animal care and use committee review. An in vitro bovine liver model perfused with autologous blood via the portal vein at three flow rates (60, 80, 100 mL/min per 100 g of liver) was used. Four ablations, two bipolar and two monopolar (control probe), were made in each of five livers perfused at each flow rate. Short- and long-axis diameters were measured from gross specimens, and volume and sphericity index were calculated for each ablation. A general linear mixed model accounting for correlation within the liver was used to evaluate the effects of flow on ablations. Analyses were performed by using software. Results: There was no significant difference in the size or shape of ablations created by the bipolar device at the different flow rates (P >.05 for all outcomes). The monopolar device demonstrated the expected inverse association between ablation size and change in flow (P<.01 for all outcomes). The mean ± standard deviation of short-axis diameter, long-axis diameter, volume, and sphericity index of the bipolar ablations was 4.3 cm ± 0.1, 4.2 cm ± 0.1, 41.0 cm3 ± 1.8, and 1.1 ± 0.1, respectively. Conclusion: Unlike monopolar RF ablation, change in portal vein flow rates does not have a statistically significant effect on the size or shape of ablations created by the bipolar RF ablation device tested.