The arterial switch operation is judged the best palliative operation for neonates with transposed great arteries. We aimed to assess the value of analysing a large series of unselected cases by this technically demanding operation and formulate a realistic prognosis. We reviewed all 432 neonates (mean age at operation 7 days, mean weight 3.25 kg) who underwent an arterial switch operation between 1987 and 1999. Follow-up (mean time: 4.9 years) was complete in 412 patients. Survival probability and freedom from reoperation was 94% and 78% at 10 years, respectively. 26 patients died, 16 because of myocardial ischaemia. Risk factors for death included early experience, low weight, associated cardiovascular malformations (especially hypoplasia of the right ventricle or aortic arch), and difficult patterns of coronary arteries. The risk of the coronary artery pattern was greatly reduced in those who had recent operations. At last follow-up, 90% of patients had normal life without treatment, and 94% a normal heart function on echocardiography. The arterial switch operation in neonates achieves excellent results mid-term. Obstruction of the translocated coronary arteries is responsible for most deaths and a substantial number of reoperations. Although confirmation is needed, these results allow anticipation of a favourable long-term prognosis.