Abstract: AIM: To investigate the influence of premature beats on atrial conduction velocity (ACV) and age-related changes in patients. METHODS: Thirty patients who had no organic or structural disease and who were treated with electrophysiological and radiofrequency ablation for AVRT or AVNRT were included in the study. The patients were divided into groups by age and the inducibility of atrial fibrillation (AF), respectively. P-wave duration and conduction time were measured between high lateral right atrium (LRA) and distal CS (iaCT) in sinus rhythm. Atrial effective refractory period (AERP) at the distal coronary sinus (CS) and high LRA at the cycle length of 600, 500, 400 and 300 msec and ACV along the CS and LRA at S1 pacing and different coupling interval premature atrial complex were also measured. RESULTS: Sustained AF was induced in nine patients. Inducibility of AF in elderly patients was 60%, much higher than in young patients. In patients with induced AF, iaCT was much higher than that of patients without induced AF (P<0.05). ACV at premature atrial complex was much slower than basal pacing (P<0.01). Age was associated with an increase in P-wave duration and a decrease in ACV (P<0.05). CONCLUSION: Aging is associated with increased P-wave duration and inducibility of AF. ACV at premature atrial complex is much slower than basal pacing, especially in elderly patients.