Aims Transient ST-T elevation (STE) is a rare complication that occurs during transseptal catheterization. This study aims to delineate the incidence and characteristics of transient STE during transseptal catheterization for atrial fibrillation (AF) ablation. Methods and results Consecutive patientswhounderwent fluoroscopy-guided transseptal catheterization for circumferential pulmonary vein radiofrequency ablation in Beijing AnZhen Hospital from January 2006 to January 2013 were enrolled in this study. Out of 2965 patients with a total of 3452 transseptal catheterization procedures, 13 patients (0.38%, mean age 57 +/- 8, 6 female, 12 paroxysmal AF, mean left atrial diameter 35.4 +/- 3.8 mm) had STE. ST-T elevation occurred after transseptal puncture in 10 patients and after pulmonary vein venography in three patients. Systolic blood pressure (129 +/- 10 vs. 104 +/- 20 mmHg, P < 0.001), diastolic blood pressure (78 +/- 6 vs. 64 +/- 11 mmHg, P < 0.001), and heart rate (83 +/- 19 bpm vs. 64 +/- 23 b.p.m., P = 0.022) significantly decreased when STE occurred. Eleven patients complained of chest pain, one patient complained of dizziness, and one patient had no symptoms. Patients recovered in about 4.6 min (2-10 min) with dopamine or fast saline drip. Catheter ablation of AF was completed in all the 13 patients without sequelae or other complications. Four of the 13 patients (30.8%) had recurrence of AF after a mean follow-up of 21.7 months. Conclusion ST-T elevation is a rare complication associated with transseptal catheterization without sequelae. Catheter ablation of AF could be safely completed in these patients.