The mechanism behind the female preponderance for atrio-ventricular node reentrant tachycardia (AVNRT) is not clear. We compared baseline electrophysiological measurements and clinical data in 141 consecutive patients (96 women) who underwent successful AVNRT ablation at their fi rst therapeutic procedure. Women had on average 9% higher resting heart rate than men (p<0.05), but were similar in all measures of AV node function. Isoproterenol infusion was required for AVNRT induction in 69 cases (49%), and the need for isoproterenol was associated with lower resting heart rate and longer anterograde and retrograde AV node refractory periods (p<0.05 for comparisons), but not with sex. We conclude that the spectrum of baseline AV node physiology in AVNRT patients is wide, and is similar in men and women. The female preponderance for AVNRT cannot be explained from comparisons of baseline AV node electrophysiological properties.