Slow decomposition of L-ascorbic acid, carried out under aerobic conditions and in the presence of cadmium ions, results in formation of a crystalline product that is highly insoluble in water. This compound has been identified as a cadmium oxalate polymeric species with formula Cd(C2O4).3H(2)O. The crystal structure of this compound is described. Relevant crystal data are the following: C4H12O14Cd2, fw = 508.94; triclinic; space group P1 (No. 1); a = 6.010(1) Angstrom, b = 6.668(1) Angstrom, c 8.498(1) Angstrom; alpha = 74.64(1)degrees, beta = 74.25(1)degrees, gamma = 80.91(1)degrees; V 314.7(5) Angstrom(3); Z = 1.