OBJECTIVE: To evaluate the feasibility of the arterial switch for surgical repair of transposition, defined as the combination of concordant atrioventricular and discordant ventriculo-arterial connections, after late referral. METHODS: From March 2000 to August 2001, six children underwent an arterial switch procedure following left ventricular preparation because of late referral. The mean age at referral was 8.3 months, with a range from 3 to 25 months, and mean body weight was 5.3 kg, with a range from 3.7 to 9.3 kg. The mean saturation of oxygen was 57%, with a range from 50 to 72%. Associated defects included a restrictive ventricular septal defect in three patients, aortic coarctation in one, and partially anomalous pulmonary venous connection in one. The mean interval between referral and the arterial switch procedure was 3.7 months, within a range from 1 to 7 months. A mean of 1.5 surgical procedures were undertaken to prepare the left ventricle, the most being 3 procedures, including combinations of creation of an inter-atrial communication in four patients, banding of the pulmonary trunk in five, and creation of a systemic-to-pulmonary arterial shunt in three. We evaluated left ventricle ejection and shortening fractions, left ventricular diastolic diameter and volume, right and left ventricular wall thicknesses, and the ratio of right to left ventricular values by echocardiography at referral, immediately before, and one week after the arterial switch procedure. RESULTS: All children are alive and well, with a mean follow-up of 17 months, ranging from 9 to 26 months. Echocardiography showed a statistically significant decrease of the ratio between right and left ventricular wall thicknesses, from 1.33 +/- 0.26 at referral to 0.79 +/- 0.08 before the switch procedure (p < 0.005). Left ventricular function was adequate after arterial switch, with a mean ejection fraction of 79.3%, ranging from 66 to 87%, and a mean shortening fraction of 41.7%, ranging from 30 to 49%. CONCLUSIONS: Despite late referral, and initially inadequate left ventricular volume and mural thickness, children with transposition can successfully be treated with the arterial switch procedure, provided that the left ventricle is adequately prepared, using echocardiography to monitor left ventricular morphology and function.