A range of diazonium salts and their corresponding triazenes have been prepared in order to directly compare their relative thermal stabilities from differential scanning calorimetry (DSC) data. A structure-stability relationship (SSR) has been explored to investigate trends in stability, depending on the aromatic substituent and the structure of the secondary amine component of the diazonium salts and triazenes.All triazenes investigated show significantly greater stability (in many cases stable above 200 °C) compared to the corresponding diazonium salts, which show varying stabilities.