Abstract: A radio frequency generator and pump apparatus for cooled ablation for ablating tissue in the wall of the heart of a patient. An ablation catheter comprising a flexible elongate member has proximal and distal extremities. An ablation electrode. is carried by the distal extremity. An electrical conductor is carried by the flexible elongate member and is coupled to the ablation electrode. A radio frequency generator is coupled to the electrical conductor. The flexible elongate member has a liquid carrying lumen extending from the proximal extremity to the distal extremity and opens into the cavity of the ablation electrode. A pump is coupled to the liquid lumen for supplying a cooling liquid to the lumen and to the ablation electrode.