Corrected transposition of the great arteries was found in a 40 year old man with congestive heart failure and complete heart block. Treatment with an implanted artificial pacemaker resulted in temporary subjective improvement, but hemodynamic measurements essentially were unchanged and the patient eventually died with congestive heart failure. Autopsy disclosed, in addition to corrected transposition of the great arteries, multiple small pulmonary emboli and an abnormality of the left atrioventricular valve. This report illustrates the natural history of corrected transposition in an adult patient. © 1969.