Two patients with coarctation of the aorta initially had acute idiopathic pericarditis with anterior pleuritic chest pain as the chief complaint. A pericardial friction rub was present in both patients. Both patients died suddenly. At autopsy, they were found to have a dissecting aneurysm of the ascending aorta with extension into the pericardial space; acute pericardial tamponade was the cause of death. We recommend that when a patient with coarctation of the aorta is admitted with pericarditis, aortic dissection should be considered and appropriate diagnostic procedures undertaken. In all young patients with acute pericarditis there should be careful palpation of the femoral pulses and review of the chest x-ray film for rib notching.