The effects of pre irradiation with γ-ray prior to thermal decomposition on the induction period of hexammine cobaldt (III) chloride have been investigated. The results indicated that the induction period of the investigated salt is shortened by exposure to γ-irradiation. Specifically the induction period I is related to the radiation dose by the equation I = C1+ C2log Φ, where C1and C2are constants. It is concluded that pre-exposure to ionizing radiation increases the number of nuclei that are active in salt breakdown in direct proportion to the γ-dose to which the sample had previously been exposed.