Background : Sinus pause is intermittently recorded paroxymal atrial tachycardia and atrial fibrillation(AF) patient. This suggest that sinus node is affected by rapid atrial stimulation. Some report shows that sinus node suppressed by rapid atrial and ventriclular stimulation. However short term Zone II atrial paicing to evaluate sinus node function in human is rare. Method: The study group is none sinus node disease who is AVNRT(atrioventricular nodal reentrant tachycardia) and AVRT(atriovenricular reentrant tachycardia) patient. The study number is 10 (male/female: 6/4) and study is performed before EP(Electrophysiological)study and ablation therapy. Anti-arrhythmic agent is stopped for three days before study. Pre pacing SNRT, CSNRT is measured at high RA. and SACT(sinoatrial conduction time) is also measured at high right atrium (RA) by Narula method. The decremental pacing is performed by 20 msec from basal cycle length to determine Zone II. Short term pacing is done for 10 min using Zone II (midportion) pacing cycle length. Post pacing SNRT,CSNRT,SACT is measured again after Zone II atrial pacing by same method. Result: Pre-pacing value of SNRT,CSNRT,SACT is 1102짹206 msec, 205짹78 msec, 151짹69 msec and post-pacing value is 1150짹318 msec, 272짹142 msec, 131짹70 msec. P value of paired T test is 0.35, 0.15, 0.08. Conclusion: There are no statistical difference between pre and post pacing SNRT, CSNRT, SACT values. This suggest that sinus node function is not affected short Zone II short term atrial pacing in non autonomic block status. This mesns that Sinus node dysfunction is involved more complex mechanism in paroxysmal atrial tachycardia and AF.