We describe a delayed, life-threatening complication in a boy operated on using the Nuss-procedure 2 months earlier. On admittance he was in shock with cardiac tamponade. An immediate needle aspiration of blood from the pericardium was done before a median sternotomy. The Nuss-bar was removed, and we identified a 1.5-cm laceration in the adventitial layer of the ascending aorta as the source of bleeding. The tear was closed, and the patient had an uneventful recovery. Careful positioning of the bar is necessary to avoid complications. Measures must be taken postoperatively to confirm that the steel bar does not rotate.