Bioprosthetic tissues are treated by immersing or otherwise contacting fixed,unfixed or partially fixed tissue with a glutaraldehyde solution that haspreviously been heat-treated or pH adjusted prior to its contact with thetissue. The prior heat treating or pH adjustment of the glutaraldehydesolution causes its free aldehyde concentration to decrease by about 25% ormore, preferably by as much as 50%, and allows a "stabilized" glutaraldehydesolution to be obtained at the desired concentration and pH for an optimalfixation of the tissue at high or low temperature. This treatment results in adecrease in the tissues propensity to calcify after being implanted withinthe body of a human or animal patient. The heat-treated or pH adjustedglutaraldehyde solution may, in some cases, also be used as a terminalsterilization solution such that the calcification-decreasing treatment withthe previously treated glutaraldehyde and a terminal sterilization may becarried out simultaneously and/or in a single container.
