Ring-substituted arylammonium sulfates (RSAS) having electron donating or attracting substituents have been prepared and characterized. Thermal decomposition studies were carried out by TG, DTG and DTA techniques. Log k and decomposition temperatures (T-d) were found to have a linear relationship with pK(a) values of the corresponding arylamine. Hammett equation gave positive value of p (Hammett substituent constant), which indicates that the decomposition is facilitated by electron demanding substituents. The proton transfer process seems to be the primary rate controlling step in the decomposition of these sulfates.