Buckling of the innominate artery implies elongation, tortuosity and dilatation of this vessel. It may cause a right superior mediastinal prominence simulating other mediastinal conditions such as tumor, aneurysm, or substernal thyroid. The buckled innominate artery is of no prognostic significance and therefore its correct identification will eliminate needless operation. It should be especially sought for in individuals with hypertension and arteriosclerotic disease who have right superior mediastinal widening on conventional X-rays. Angiocardiography will establish the diagnosis in such cases.