The standard view of blood coagulation is based on a mechanism whereby cascade interactions of clotting factors generate thrombin, which converts soluble fibrinogen into an insoluble clot.An alternate process is operative that can transform fibrinogen, based on reactions with free
radicals. Such could be generated by the release of ascorbate by activated platelets. Ions of multivalent metals, such as Cu+2 or Fe+2 bound to fibrinogen, react with the ascorbate (a reductant in a Fenton reaction) to generate H2O2 and reactive oxygen species. Alternately, γ-irradiation which generates H2O2 could generate such species. Supportive evidence and references are cited.