Six di-ortho-substituted arylammonium sulphates (di-o-SAS) have been prepared and characterised. The thermal decomposition of these salts was investigated by TG, DTA and DSC techniques and kinetics evaluated using mechanisms based on the kinetic equations. The parabolic law equation was found to give the best fits based on the correlation coefficients. An activation energy (35-75 kJ mol(-1)) for the decomposition of di-o-SAS was found to be less than dianilinium sulphate (118 kJ mol(-1)) and the meta- and para-substituted salts. It seems that the basicity is lowered by steric effects in di-o-SAS and the decomposition rates are enhanced. A reaction scheme representing the thermal decomposition pathways of these salts has also been proposed.