Simultaneous TG (thermogravimetric analysis)-DTA (differential thermal analysis) measures both differential temperatures and weight changes in a material as a function of temperature or time in a controlled atmosphere. Simultaneous measurement of these two material properties not only improves productivity but also simplifies interpretation of the results. The complementary information obtained allows differentiation between endothermic and exothermic events which have no associated weight loss (e.g. melting and crystallization) and those which involve a weight loss (e.g. degradation). The combined evaluation also assures identical experimental and sampling conditions for both measurements, thereby eliminating those sources of uncertainty. This paper briefly describes a new simultaneous TG-DTA instrument with emphasis on how the measurements are made and with several typical applications