The thermal decomposition of m-ditoluidinium sulfate (m-DTS) has been studied and 2-methylsulfanilic acid (2-MSA) has been found to be the decomposition product. Isothermal TGA data on m-DTS were fitted in Avrami-Erofeev (n= 2, 3), Contracting area. Contracting cube and Ginstling Brounshtein equations. The Contracting cube equation was found to give the best fit and the mean value for the energy of activation for m-DTS decomposition is 31 ± 1 kcal mol^{â 1}. The proton-transfer process seems to be the primary step during decomposition of m-DTS.