Peyronie's disease (PD) affects the tunica albuginea of the penis with a formation of dense and fibrous plaques. The plaques can cause a variety of symptoms in the patient such as pain during erection, erectile dysfunction, and penile disfigurement. There are many treatment options available, though none without disadvantages. Quantification of the material properties of the tunica tissue can inform potentially improved treatments. In this study tunica tissue (n=5) from donors were tested biaxially along the circumferential and longitudinal directions to a specified load magnitude and maintained at a fixed displacement for 30 minutes to allow for stress relaxation. The loading and relaxation were then repeated for a second time. Stiffness, Young's Modulus, strain at inflection point between the toe region and linear region on the stress-strain curve, as well as percent stress relaxation after 30 minutes were compared between anatomic directions and ramp number. Only stiffness and percent relaxation showed a statistically significant difference between ramps 1 and 2, regardless of direction (p = 0.012). The results from this study report the baseline data of the biaxial mechanical properties of the tunica albuginea to be used for future comparisons to the properties of PD and graft tissue. / Master of Science / Peyronie’s disease (PD) affects a layer of tissue in the penis known as the tunica albuginea. Dense and fibrous plaques form on this layer which can cause pain during erection, erectile dysfunction, and penile disfigurement. There are many treatment options available, though none without disadvantages. In this study tunica tissues from donors were tested in order to find the material properties of the tissue to improve treatments. The tissue samples were pulled in tension in two directions simultaneously to a specified load magnitude and then held at a fixed displacement for 30 minutes. This protocol was then repeated a second time. The material properties of the tissue were compared between the anatomic directions of the tissue was well as protocol number. The results from this study report the baseline data of the biaxial mechanical properties of the tunica albuginea to be used for future comparisons to the properties of PD and graft tissue.