Gamma irradiation was found to release iodine in small amounts from powdered samples of cesium iodide and barium iodide, but not from zirconium iodides. The amount of iodine released was measured with silver foil detectors in sealed capsules that contained the salt. The amount of release was markedly affected by impurities, especially water, that were difficult to control; therefore, G values calculated were inaccurate but of the order of 10−3 atoms of iodine released for 100 eV of energy absorbed for CsI and BaI2 near room temperature. The G values for the zirconium iodides were much smaller. The phenomenon of release of iodine from the ionic iodides by gamma radiation is discussed on the basis of published theories of the formation of defects in solids.