Changes in the dimensions of the thoracic aorta with age were studied in 70 healthy volunteers between the ages of 10 and 83 years. Spin echo images were acquired at end-diastole in three oblique planes through the ascending aorta, aortic arch, and descending aorta. A double oblique image through the whole of the thoracic aorta was also acquired. Measurements of aortic cross-sectional area and length were corrected for body surface area, and normal magnetic resonance standards were established. The direct correlation that aortic dimensions have with age is likely to be due to loss of elasticity. The ratio between areas of the ascending aorta and the aortic arch is directly related to age whereas the ratio between the aortic arch and the descending aorta is inversely related to age.