Bioprosthetic heart valves based on animal tissues, primarily bovine pericardium, is one of the choices for heart valve replacement surgery that allows the patient to lead a relatively normal life. However, this type of heart valve has only limited durability. Tissue calcification is among the factors that have been identified which contribute to its failure. Approaches to reduce soft tissue calcification have been investigated and the addition of a dimethyl sulfoxide treatment step to the tissue crosslinking process has been demonstrated to be effective. Additional work is in progress to further understand the underlying mechanism to calcification reduction with an ultimate goal to develop a bioprosthetic heart valve of increase the durability.