The recording of intracardial electrocardiograms (IECG) has made good progress in the arrhythmology during last 15 years. First the aim was to describe the characteristics of the conduction system of the heart (Hisogram recording), followed by the evaluation of pathologies of the conduction system (meaning bradyarrhythmias), electrical activation of the myocardium when tachyarrhythmia is ongoing for diagnosis and punctual localization of accessory pathways during endocardial mapping. The next logical step as a reaction to the knowledge of endocardial mapping was the evaluation of new therapeutic methods--DC followed by radiofrequency ablations--nonpharmacological therapeutic antiarrhythmic procedures, usually used in electrophysiology labs of cardiological departments. Nowadays pacemakers are equipped with possibilities of intracardial atrial and ventricular signal recording which enables the use of accesorial antiarrhythmic functions. Intracardial electrocardiogram recording plays the dominant role in implantable cardioverter-defibrillators, where the main part of algorithms for detection and discrimination is based on the electrocardiograms. From both the diagnostic and therapeutic points of view intracardial signal recording is playing an important part in clinical practice in arrhythmology these days.