When radiofrequency catheter ablation of ventricular arrhythmias is unsuccessful, an option may be to combine it with direct current energy. We therefore investigated the effects of such a combination. Radiofrequency energy was delivered in a bipolar or unipolar fashion to the left and right ventricles through an ablation catheter with a tip electrode 2 mm long, using a temperature-guided radiofrequency generator. Radiofrequency ablation was followed by a single cathodal direct current shock (66 J) with the ablation catheter positioned similarly in six closed-chest pigs. In a control group (six animals) only direct current ablation was performed, with one or two energy applications (66 J) in each ventricle. Two of six animals in the radiofrequency/direct current group died due to perforation in the follow-up period, 1 and 3.5 h after the direct current ablation, respectively. Gross pathological examination of the hearts revealed transmural lesions in all animals. In the radiofrequency/direct current group four lesions were perforated, three of which were located in the left ventricle. There was a significant increase in the number of perforations in the radiofrequency/direct current group compared to the control group, where perforation was never observed. Haemorrhagic pericardial fluid was found in five of the six animals in the radiofrequency/direct current group compared to none in the control group. These findings show that myocardial ablation with radiofrequency energy followed by direct current energy in the same session may have a high complication rate.