Sixty-nine patients with Corrected Transposition of the Great Arteries were studied, with a mean age of 8.3 years. Forty-nine had atrial situs solitus (SS) and 20 atrial situs inversus (SI). The diagnosis was proved by echocardiography in 28 cases and in all by angiocardiography. In cases with SS, 29 presented ventricular septal defect (VSD), 20 had subvalvular pulmonary stenosis (SVPS), 13 tricuspid regurgitation (TR), 13 atrio-ventricular block (AVB), and seven without associated defects. In cases with SI, 13 had VSD, 14 SVPS, five IT, three AVB, and two without associated defects. The long-term follow-up of the atrioventricular (AV) conduction in 53 cases, ranging between 2 and 37 years (mean 8.3) showed at the beginning of the evaluation 37 cases with normal AV conduction, 14 with first degree AVB, and two with complete AVB. At the end of the follow-up 24 cases had normal AV conduction, 13 first degree, two second degree, four intermittent and 10 complete AVB. The contingency table showed that the possibility of developing changes of the AV conduction was greater in those cases who had an abnormality at the beginning with a relative risk of 2.27 (p = 0.03). Twenty-three cases had SVPS associated with VSD without significant symptoms. During a follow-up ranging from 1 to 20 years (mean 6.5 +/- 5.9), five of these patients were surgically corrected at ages from 6 to 11 years. The remaining cases have had a stable course. At the beginning of the study, 18 cases had TR, and it developed in five more patients during the same follow-up period.(ABSTRACT TRUNCATED AT 250 WORDS)