Background: Health-related quality of life in adults with congenital cardiac disease appears to be impaired, but the determinants of this alteration remain largely unknown. The aim of our study was to examine the impact of arrhythmias on quality of life in patients late after the atrial redirection operation for transposition, or after complete correction of tetralogy of Fallot. Patients and methods: We enrolled 32 patients with transposition, and 35 patients with tetralogy of Fallot, in a prospective study. Quality of life was assessed using RAND-36 questionnaires. Quality of life data were compared with those of an age-matched control population. Patients underwent 24-hour and 7-day electrocardiographic recordings, echocardiography, and exercise testing. Results: Patients without arrhythmias had quality of life comparable to that of the general population. All 8 domains in the questionnaire showed scores 22 to 51 percent lower in 12 patients with atrial tachyarrhythmias, and/or sinus nodal dysfunction, requiring insertion of a pacemaker in comparison with 55 patients without arrhythmias. In patients with transposition, low scores were not only associated with arrhythmias, but also correlated with impaired exercise capacity. Conclusions: Atrial tachyarrhythmias, and sinus nodal dysfunction, requiring insertion of a pacemaker, were associated with impaired quality of life in adults late after atrial surgical correction of transposition or correction of tetralogy of Fallot.