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Ablation of fractionated electrograms (EGMs) has been performed to eliminate areas of slow conduction in atrial fibrillation (AF). The rotor hypothesis suggests that rapidly activating spiral waves perpetuate and maintain AF. This study describes the EGM characteristics of AF rotors, using the novel 64-electrode basket catheter.Twenty-five patients (male n = 16) with AF (paroxysmal n = 10) underwent focal impulse and rotor modulation. A 3.5 mm irrigated-tip ablation catheter was placed at the identified rotor core and EGMs were analysed for amplitude, characteristics (single-EGM, fractionated-EGM, and continuous-EGM), and cycle length over 10 s. A total of 72 rotors were identified [right atrium (RA) = 13, left atrium (LA) = 59]. Seven rotors were excluded from EGM analysis due to location in the pulmonary veins. Single-EGMs were more frequent in the RA compared with the LA (8 (61.5) vs. 12 (23.1); P < 0.01) and EGM amplitudes were smaller in LA rotors when compared with RA rotors (0.14 (0.08–0.17) mV vs. 0.19 (0.15–0.29) mV; P = 0.029). In patients with persistent AF, single-EGMs were observed more often in the right-sided rotors compared with left-sided rotors (4 (57.1) vs. 5 (14.3); P = 0.012), and EGM amplitudes were smaller in patients with persistent AF compared with paroxysmal atrial fibrillation (PAF) patients (0.15 (0.09–0.19) mV vs. 0.22 (0.17–0.47) mV; P = 0.03). Furthermore, the prevalence of fractionated- EGMs was higher in patients with persistent AF compared with PAF patients (31/42 (73.8) vs. 9/23 (39.1); P = 0.03).There are no characteristic rotor-EGM potentials. Rotor-EGM characteristics are different between the RA and LA. Although rotors are not associated with abnormal EGMs, rotor-EGMs in persistent AF were more fractionated with lower amplitudes compared with that in PAF.