Effect of gamma-irradiation on the electrical resistivity of high volatile bituminous Hariajam coal has been investigated at different temperatures. Gamma-irradiation causes a significant change in the electrical resistivity, showing firstly a decrease up to 150 Mrad and then beyond this dose a significant increase at all temperatures, the increase being more pronounced at 800-degrees-C. The results have been explained on the basis of cross-linking and/or degradation of polyaromatic groups in the macromolecular structure of coal caused by gamma-rays.