The purpose of this study was to investigate the cardiological health status and health-related quality of life after the arterial switch operation (ASO) for transposition of the great arteries (TGA) in comparison with a normative reference group. Chart review and cross-sectional systematic follow-up, including echocardiography, exercise testing, and electrocardiography, were performed on all survivors of ASO for TGA between 1990 and 1995. Health-related quality of life (HRQOL) was assessed using a standardized questionnaire. A normative reference group was included. Forty-nine survivors [median age at operation 13 days, mean age at follow-up 11 +/- 2 years (37/49 with intact ventricular septum] were identified. Thirty-three of 49 patients (67%) [22/33 TGA with intact ventricular septum (IVS)] participated in cross-sectional follow-up. Cumulative 10-year event-free survival was 88% and the re-intervention rate 6%. Aortic root dilatation occurred in 70% of patients; none had severe aortic regurgitation. Left ventricular function was normal. Exercise performance (85% of reference capacity, p = 0.02), maximal oxygen uptake (85%, p < 0.01) and peak heart rate (95%, p < 0.01) were decreased. Exercise electrocardiogram was normal as was rhythm status. Unfavourable outcomes on HRQOL were found for motor functioning and positive emotional functioning. Overall there were no significant differences between TGA/IVS and TGA/VSD. We conclude that at mid- to long-term follow-up after ASO, major events and re-interventions (6%) occur infrequently. Exercise capacity and maximal oxygen uptake are lower than those in a reference population, which could not be related to diminished ventricular function. Aortic root dilatation is frequent, irrespective of the anatomical subgroup. Severe aortic regurgitation or left ventricular dilatation was not found. The unfavourable health-related quality of life deserves further attention.