A method of treating a biological tissue including contacting the biological tissue with an aqueous sterilizing solution, and maintaining the aqueous sterilizing solution at a temperature of about 50.degree. C. for a time period of about 1 to 2 days. The method of treating a biological tissue may be utilized as a terminal sterilization step in a method for fixation of biological tissues, and bioprosthetic devices may be prepared by such fixation method. The fixation method may include the steps of A) fixing the tissue, B) treating the tissue with a mixture of i) a denaturant, ii) a surfactant and iii) a crosslinking agent, C) fabricating or forming the bioprosthesis (e.g., forming the tissue and attaching any non-biological components thereto) and D) subjecting the bioprosthesis to the terminal sterilization method. The aqueous sterilizing solution may be glutaraldehyde of about 0.625 weight percent buffered to a pH of about 7.4.