Samples of descending mid-thoracic aortas were obtained from human autopsies and experiments were performed to determine the effect of strain rate and direction of loading on the failure properties of the tissue in uniaxial tension. The tests were performed at quasi-static strain rates in the range 0.01 s-1-0.07 s-1 and dynamic tests in the range 80 s-1-100 s-1. Ultimate stress and extension ratio values have been calculated for specimens tested in the longitudinal and transverse directions of the aorta.