The final product of the radiolysis of potassium trisoxalatoferrate(III) has been identified by analysis, Mössbauer and i.r. spectroscopy as the potassium salt of the dinuclear anion [ox2FeO2C2O2Fe ox2]6– which contains a quadridentate bridging oxalate group O2C2O2. This compound can also be prepared by the thermal decomposition of the salt. The role of such intermediaries as Fe ox2(H2O)22– and other oxalatoferrates is established and a mechanism for the radiolysis discussed. The G value for the decomposition, 7·1 is exceptionally large for the radiolysis of an inorganic solid.