The thermal dehydration and decomposition of Co-60-gamma-irradiated and non-irradiated crystals of manganese acetate tetrahydrate were studied using dynamic thermogravimetric techniques. The effects of radiation on the kinetics of the thermal decomposition reactions were studied up to a total dose of about 700 kCy. A computer program has been used for kinetic evaluation of non-isothermal thermogravimetric data according to a composite integral method, Kinetic analyses of dynamic TG curves were discussed in view of the composite method in comparison with the methods due to Coats and Redfern and to Ozawa. The activation parameters of the decomposition reactions for non-irradiated and gamma-irradiated crystals were calculated and the results of the different methods of data analysis were compared and discussed.