Decomposition of barium perchlorate occurs through various stages: (i) initial gas evolution, (ii) induction period, (iii) short acceleratory, and (iv) long decay. Effect of pre-irradiation with60Co -rays (5 to 100 Mrad) on the decomposition process between 703.0 to 733.0 K shows that irradiation reduces the duration of induction periodI to the onset of reaction conforming to the relation:I=C1-C2 log dose. The experimental data forI are very close to the theoretical values obtained by using the induction period-dose relationship. The topochemical aspects of the validity of the above relation has been considered to be due to the linear growth of nuclei during irradiation and subsequent exponential growth during the induction period. Irradiation enhances the rate of reaction in the acceleratory stage but decreases the duration of the decay period.