In the present investigation, pyrolytic behavior of perhydrous Indian coals was evaluated using thermogravimetric analysis from 50 to 1,000 degrees C. The devolatilization was classified into five major regions of thermal activity, i.e., dehydration of water, pre-plastic region, plastic range, secondary devolatilization, and contraction region. The values of activation energies in different regions indicate to follow different mechanisms during pyrolysis. Up to 850 degrees C, different mechanisms, i.e., dehydration, desorption, devolatilization, and thermal degradation (tar and hydrocarbon formation), are the controlling steps. From 850 degrees C, consecutive reactions like dehydrogenation, condensation, and contraction of carbon planes take place. These coals are of sub-bituminous rank; however, their activation energies for various regions are found to lie within the ranges reported for bituminous coals, which is due to their perhydrous nature.