The anatomy, natural history, clinical features and symptomatology of 101 cases of congenitally corrected transposition of the great arteries (C-TGA) diagnosed over a 20-year period at Hospital for Sick Children, Toronto, Ontario, is reported. Only 1 patient had no association lesion and only 14 an intact ventricular septum. Pulmonary stenosis was present in a little more than half of the patients. Left A-V value involvement existed in 21 patients. In spite of the hich incidence of associated lesions with prognosis was better than expected. Seventy-six patients were alive at the end of the study, no one being critically ill. No death occurred among the patients with intact ventricular septum. Patients with pulmonary stenosis as a group developed symptoms later, were less handicapped and had a better prognosis than those without a pulmonary stenosis. One third of the patients had dysrhythmias. Eight patients having a 3rd degree AV-block. Auscultatory findings were not of too great a help when diagnosing C-TGA. Forty-seven patients had a single second sound, of these 37 had pulmonary stenosis. In 60% of the patients, where information was available, the second sound was reported to be of normal intensity. Our surgical experience is documented and discussed. Palliative procedures were done with successful results and low mortality. Totally corrective procedures were performed in 9 patients with 4 deaths.