A method for preparing heterogeneous graft material from animal tissue in which the harvested tissue is cleaned, chemically cross-linked and then vacuum-dried to remove substantially all moisture therefrom. The vacuum-dried animal tissue is then double-wrapped and subjected to radiation sterilization while in its packaged dry state. Electron beam sterilization is a preferred method. At the time of use, the outer wrap is opened and the inner sterile package is placed in the sterile field in the operating room. When the tissue specimen is removed from its inner wrap, it may be rehydrated in sterile saline to restore its soft, supple hand, or it may be implanted in its dry state at the implanting surgeon's discretion, in which case, the tissue would undergo rehydration with the patient's own body fluids.