This paper addresses the problem of Traumatic Aorta Rupture (TAR) that is one of the causes of fatality in motor vehicle accidents. The mechanisms that have been suggested for TAR are speculative and inconclusive and most tests performed have not been repeatable. One of the main reasons for these speculations is an incomplete understanding of the material properties of the aorta. The goal of the presented experiments is to characterize the relationship between stress and strain in the aorta wall in the biaxial pressure tests. An experimental setup was developed such that sinusoidal pressure (between 4.5 and 74.2 kPa) was supplied into porcine aorta at frequencies ranging from .5 Hz to 5 Hz. The aorta sample (n=7) was tested with both ends fixed and one end attached to the inlet tube for pressurization with normal saline solution. The deformation of aorta in the center and the pressure inside the aorta were recorded. The experimental results are represented in the form of Kirchhoff stress versus Green strain curves which show an increase in stiffness with an increase in the frequency. The curves also demonstrate that the loading and unloading paths of the aorta are different. The results of this study were then used to develop a material model of the aorta in biaxial loading conditions using the quasilinear viscoelastic theory.