Pericardia from varying mammalian species, chemically modified with a crosslinking reagent, have been used in the cardiovascular surgery as a biological patch or in the construction of heart valve prosthesis, The study was to compare the thermal stability, mechanical strength, wettability, surface tension, and resistance against collagenase degradation of the pericardia from calves, sheep, pigs, and dogs fixed with an epoxy compound, The aim was to expose an appropriate raw material to develop epoxy-fixed pericardial heterografts as alternatives to the glutaraldehyde-fixed prostheses for clinical applications, It was found that the thermal stability, wettability, surface tension, and resistance against collagenase degradation of the pericardia from four species, both before and after chemical modification, were comparable. However, the bovine pericardium appeared to have a better mechanical strength than the other species, Therefore, if mechanical strength is an issue to be taken into account for assessing the performance of pericardial heterografts, the bovine pericardium seems to be the choice of raw material for constructing the prostheses.