Information focused on elderly patients with paroxysmal supraventricular tachycardia, and a comparative study between the elderly and younger patients was limited. The aim of this study was to investigate the clinical features and electrophysiologic characteristics in elderly patients (> or = 65 years of age) with accessory atrioventricular pathway-mediated tachyarrhythmia or atrioventricular nodal reentrant tachycardia. Electrophysiologic studies of 45 elderly patients with accessory pathway-mediated tachyarrhythmia and 47 elderly patients with atrioventricular nodal reentrant tachycardia were performed. When compared with younger patients, the elderly patients had a similar incidence of critical clinical manifestation, higher incidence of other cardiac disease or systemic disease, similar inducibility of tachycardia, greater baseline electrophysiologic parameters (sinus node, atrioventricular node, atrium and ventricle), and poorer properties of accessory pathways and dual atrioventricular nodal pathways. These results suggest that conduction properties of accessory pathways and dual atrioventricular nodal pathways were poorer in elderly patients, but similar critical manifestations and tachycardia events were found in elderly and younger patients.