A left ventricular angiocardiogram for evaluation of the mitral valve in patients with uncomplicated secundum type atrial septal defect has been proposed in a recent paper by Victoria et al. (1974). These authors observed 8 children with a ballooning mitral valve and ASD II. They stressed the necessity of performing a left ventricular angiocardiogram in every patient with ASD II. To challange their proposal, the angiocardiograms of 78 children with secundum type ASD were reviewed. Of these 89 angios 34 were performed using the left ventricle (LV) as injection site while 55 times the injection was made in other parts of the heart, e.g. left atrium, pulm. art., right ventricle, right atrium. All 34 LV angios, but only 12 of the others allowed an evaluation of function and morphology of the mitral valve. Of the 46 angiocardiograms 27 (58.7%) revealed an intact, normally closing and opening mitral valve. In the remaining 19 (41.3%) various grades of ballooning or mild prolapsing of one or two leaflets of the mitral valve could be detected. The "scallops" were minimal in 12, moderate in 4 and pronounced in 3 cases. A mild regurgitation was seen in 1 patient only. No patient had the pronounced ballooning observed by Victoria et al. On auscultation only 1 case had the apical murmur of mitral regurgitation. The ECG of our 19 "positive" cases did not show signs of left atrial or left ventricular hypertrophy. A left axis deviation was found in 1 patient. During surgery no structural abnormality of the mitral valve was noted. Postoperative reevaluation of the mitral valve (including left ventricular contrast injection) in 10 cases revealed no change of mitral valve appearance in 8, a decrease of the ballooning in one, and an increase in another patient. It is concluded that prolapses of the mitral valve are seldom of such a degree as to cause dysfunction in children with secundum type ASD. The indications for performing a left ventricular injection of contrast material are the clinical signs of mitral valve regurgitation and/or left axis deviation in the ECG.