Five thermal analysis techniques (DSC, modulated DSC?, TMA, DMA, and DEA) are used to characterize the glass transition temperature (Tg) for amorphous polymers. Each of these thermal techniques detects the Tg based on changes in a different material property during the glass transition. Hence, the relative sensitivities of the different techniques for detecting the Tg vary depending on the nature of the material being evaluated as well as on experimental variables such as the heating rate. This study compares the Tg information obtained from the five common thermal techniques on a typical amorphous thermoplastic. The results illustrate the types of issues that can arise.