Abstract: A technique for the treatment of ventricular tachycardia. The ventricles are endocardially mapped by way of an electrophysiological workup. This mapping locates the tachycardial foci and other abnormalities in conduction. A special catheter containing an optical fiber is percutaneously inserted into a blood vessel and advanced into the ventricle. The distal tip of the catheter is positioned adjacent to each of the tachycardia generating sites. A medical laser is used to irradiate each site via the optical fiber. The tissue at each site is thereby photocoagulated or ablated to remove the source of the tachyarythmia.