Abstract: This invention relates, in general, to a process for cross-linking and stabilizing proteinaceous material, and in particular, to a process for oxidizing collagenous material, by oxidizing the tissue. The invention also relates to the resulting cross-linked product. The method comprises immersing the material to be cross-linked in a solution comprising compounds designed to generate the radical species singlet oxygen or other oxidizing intermediates without the addition of an external energy source. Immersing collagen containing tissue in a solution comprising an oxidizing agent and sufficient dissolved oxygen, under controlled conditions of pH and temperature, provides a cross-linked and stabilized collagen containing tissue that resists chemical and enzymatic degradation.