Aims This single-centre prospective study was designed to determine the incidence, therapeutic implications and prognosis of atrial. arrhythmias (AA) in patients with Brugada syndrome (BS). Methods and results Fifty nine consecutive patients with BS and 31 age and gender-matched controls underwent an electrophysiological. exploration and were followed-up during 34 13 months. The final AA incidence was 20% in BS patients vs 0% in controls (p < 0.01). Ventricular inducibility was significantly related to a history of AA (p = 0.02). The incidence of AA in patients with a spontaneous electrocardiogram of BS was 26% vs 10% in patients with a flecainide-induced electrocardiogram (p < 0.05). In patients with an indication of implantable cardioverter defibrillator (ICD), the incidence of AA reached 27% vs 13% in patients with BS but without ICD indication (p < 0.05). Inappropriate shocks due to AA episodes were observed in 14% of ICD patients vs 10.5% of appropriate shocks. Multivariate analysis identified the implantation of a single-chamber device as an independent predictive factor of inappropriate ICD discharges (p < 0.05). Conclusion BS patients exhibit an abnormally high proportion of AA. Our data strongly suggest a more advanced disease process in BS patients with spontaneous AA. Careful programming of single-chamber ICD should be recommended to avoid inappropriate discharges. (C) 2004 Published by Elsevier Ltd on behalf of The European Society of Cardiology.