Since the development of radiofrequency catheter ablation for the treatment of atrial fibrillation, electrophysiology laboratories have experienced a significant rise in the number of transseptal catheterization procedures. Traditionally, the procedure requires the presence of a interventional cardiologist who carries out transseptal catheterization following arterial puncture and placement of a reference pigtail catheter in the aortic root. Use of His bundle and coronary sinus catheters to provide anatomical and electrophysiological landmarks enables transseptal catheterization to be carried out without the need for arterial puncture or intracavity pressure measurement. We report our experience with transseptal catheterization in an electrophysiology laboratory using only electrophysiological landmarks. The procedure was carried out on 68 occasions and was successful in all patients except one, in whom catheterization could not be performed for anatomical reasons and because the patient had previously received anticoagulation therapy. One other patient developed transient ST elevation, which was probably due to an air embolism.