Thermal stability of polyaniline was evaluated to assess its use as ion-exchanger at elevated temperatures. Thermogravimetric analysis of salt (chloride) and base form of polyaniline revealed the decomposition pattern and volatile products. Structural modifications in PAni upon heating upto 500°C were studied using UV –vis spectroscopy, Fourier Transform Infrared spectroscopy, and viscometry. The gaseous decomposition products of polyaniline were identified using high resolution infrared spectroscopy for the first time. Anion exchange capacity of polyaniline, in terms of ionisable chlorine, determined using Energy Dispersive X-ray Fluorescence spectrometry, was found to be 3.25 meqg^-1 . Polyaniline was found to retain ~90% of the original capacity on heating upto 200°C. These studies evinced the superior thermal stability of polyaniline over conventional anion exchangers.