The reduction of oxyiron(V), (FeO43-)-O-v by inorganic oxysulfur species (SO32- and S2O32-) has been anaerobically in alkaline medium by using a premix pulse radiolysis technique. Studies on the reactions of (FeO42-)-O-VI with the two sulfur radicals were also carried out. The spectroscopic results demonstrated that sulfur radicals reduced (FeO42-)-O-VI to (FeO43-)-O-V which is subsequently reduced by oxysulfur species by a two-electron reduction step to Fe(III). The rate constants for reduction of (FeO42-)-O-VI to (FeO43-)-O-V by sulfite and thiosulfate radicals ((SO3-)-S-center dot and S4O6 center dot 3-) were found to be (1.9 +/- 0.3) x 10(8) and (7.5 +/- 0.8) x 10(7) M-1 s(-1), respectively, However, the reactions of (FeO43-)-O-V with the SO32- and S2O32- ions were separated by an order of magnitude, with SO32-reacting at (3.9 +/- 0.3) x 10(4) M-1 s(-1) while S2O32- reacted with Fe(V) at (2.1 +/- 0.1) x 10(3) M-1 s(-1) at pH 11.4.