Heart valve disease is currently one of the leading forms of heart disease. Current literature has shown that endothelin I, angiotension II and 5-HT are vasoactive agents which cause concentration dependent contractions in aortic valve leaflet tissue. This study tested the mechanical properties of leaflets cut in the radial direction after they were exposed to the agents at varied concentrations or for 0.5, 6 or 24 hours. The elastic modulus, ultimate tensile strength and the yield strength were calculated. In the time trials the elastic modulus and the ultimate tensile strength both showed a significant increase at 24-hours. However, there were no significant differences found between the concentrations. Indicating the amount of vasoactive agent is not as significant as the length of exposure.