Physiologic pacemakers offer hemodynamic benefits in comparison to conventional pacing, but demand more detailed diagnosis of the arrhythmia in need of treatment. In order to prevent endless loop tachycardias, ventriculoatrial conduction must be analyzed. Normal sinus node and atrial function should be confirmed in atrial triggered ventricular stimulation. The techniques and values of preimplantation investigations, including intracardiac electrophysiological procedures, are discussed.