The glass transition temperature of a polymer is normally reported at a single temperature. The fact that the reported glass transition temperature is dependent on heating rate and frequency has sound theoretical support. It has been observed that there is a great deal of information derivable from the shape of the glass transition region. Examples are given of the effect of polymer preparation, cure mechanism, component compatibility, and cure history on the glass transition region. The relationship between the dynamic mechanical properties and polymer performance is also discussed. -- AATA