Systemic right ventricular dysfunction has been closely linked to late mortality and sudden cardiac death in patients with Mustard procedure for dextrotransposition of the great arteries. Two young patients with dextrotransposition of the great arteries late after Mustard procedure who presented with acute transmural myocardial infarction and sudden cardiac death (one patient) without prior exertional angina or causative coronary abnormalities are reported. It is surmised that acute coronary emboli originating from a severely dilated, hypocontractile systemic ventricle were the cause of transmural myocardial infarction. This phenomenon may be an important and as yet unrecognized factor in late morbidity and mortality in such patients.