Differential scanning calorimetry (DSC) has been used to investigate the thermal transitions occurring for a series of Argonne Premium Coals. Two sets of experiments were conducted using different heating profiles to further examine a Second-order transition which had previously been observed for Illinois No. 6 coal. Thermogravimetric analysis (TGA) was also conducted on the samples to support the DSC data. The DSC results show that on initial heating a first-order transition is observed which is a function of the cooling cycle and that subsequent scanning shows a clear and reproducible second-order process with the characteristics of a glass transition process. TGA shows that no mass loss, is associated with either of these transitions.