Two hundred consecutive patients undergoing resection surgery of the lung during 1999 were retrospectively reviewed to define prevalence, type, clinical course and risk factors for postoperative supraventricular arrhythmias (SVA) with particular reference to atrial fibrillation or flutter (AF). Records of 200 lung patients were collected and analysed with particular attention to preoperative physiologic values and associated pathologies, lung functional status, electrocardiogram registration, extent of surgical resection of the lung and were also analysed to confirm or exclude correlation between them and postoperative AF; three patients were excluded as they were affected preoperatively by SVA. Forty-five episodes of SVA, 41 of AF were identified in 197 patients (22%) and were more prevalent in several groups of patients such as those with increased age, pneumonectomy and superior lobectomy. Rhythm disturbances were most likely to develop on the second day after surgery. Ninety-eight percent of AF disappeared within a day of discharge and sinus rhythm was restored with digitalis or other antiarrhythmic drugs in all patients except one who was discharged with persistent atrial fibrillation. Arrhythmias were not direct causes of any in-hospital deaths. There is a tendency in the difference of the AF rate between pneumonectomy and upper lobectomy patients versus inferior lobectomy ones, probably related to the different anatomic structure of the proximal trunks of the upper and inferior veins of the lung, respectively. Statistical analysis revealed that increased age, extent and type of pulmonary resection, such as pneumonectomy and superior lobectomy were significant risk factors. Despite these factors, arrhythmias after lung surgery could be managed easily and were not closely related to higher mortality. Direct cause of AF after lung resection surgery remains unclear; anatomical substrate such as surgical damage to the cardiac plexus or to the proximal trunks of the pulmonary veins covered by myocardial sleeves with electrical properties are to be considered.