Three dichloroanilinium hydrogensulfate (DCAHS) and two dichloroanilinium sulfate salts were formed while treating corresponding amines with excess amount of conc. sulfuric acid. These DCAHS salts were characterized by elemental analysis and spectral data. Thermolysis of these salts has been studied by using various thermo-analytical techniques under different conditions. All the salts on heating produce corresponding dichloroaminobenzene sulfonic acids (DCABSA) as intermediate product, which on further heating decomposes into gaseous products. The DCABSA were isolated and characterized by elemental and spectral analyses. Conventional model fitting methods and a model free isoconversional method were used to evaluate kinetic parameters for isothermal TG data and an attempt has been made to compare merits and demerits of both ways of kinetic approaches. The thermal decomposition pathway has also been suggested for DCAHS salts via solid-state sulfonation involving proton transfer as primary step. (C) 2003 Elsevier Science B.V. All rights reserved.