Purpose: To determine whether and why hydrochloric acid-infused radiofrequency ablation creates larger lesions than does conventional,saline-infused radiofrequency ablation.Materials and Methods: We created 60 lesions in 30 fresh excised porcine livers,30 with acid-infused and 30 with sodium-infused ablation.Both modalities used monopolar perfusion electrode connected to a radiofrequency generator set at 103oC and 30 W.In each group,ablation time was set at 10,20,or 30 minutes (10 lesions from each group at each time).