The effect of gamma irradiation on transport properties and kinetic parameters of high-temperature ceramic Y3Ba5Cu8O18 superconductor has been investigated. The bulk samples, prepared by the standard solid-state reaction method, were irradiated by gamma rays of different doses in the range 0-44.8 kGy at room temperature. The changes in transition temperature (T c ) and excess conductivity have been discussed. The effects of irradiation on surface morphology have been investigated by scanning electron microscopy. The kinetic parameters have been estimated by thermogravimetric analysis.