This chapter presents information about various aortic diseases including normal dimensions, echo features of various diseases, and causation. Normally the aorta swings anteriorly during left atrial filling in diastole, by 7 to 15 mm. An anterior aortic swing < 7 mm indicates a low cardiac ouput state and when > 15 mm it is a marker of hyperdynamic circulation. Dilatation of the sinus of Valsalva beyond 40 mm is abnormal. An aneurysm of sinus of Valsalva appears as an outpouching of the dilated coronary sinus anterior to the anterior aortic wall protruding into the right ventricular outflow tract (RVOT). A rupture of this aneurysm into the right ventricle produces right ventricular volume overload. Aneurysm of sinus of Valsalva or the fistula created by its rupture is best visualized on transoesophageal echo. Abnormalities associated with aneurysm of sinus of Valsalva include bicuspid aortic valve, coarctation of aorta, and ventricular septal defect. Dilatation of the aortic root beyond 60 mm is observed in aneurysmal dilatation of the aorta which may be saccular on fusiform. Causes of aortic aneurysm are atherosclerosis, syphilitic aortitis, Marfan’s syndrome, post-traumatic and mycotic aneurysm.