The differential scanning calorimetry glass transition (DSC T-g), measured by ASTM test method E-1356, and the dynamic mechanical analysis glass transition (DMA T-g), measured using a new definition of the DMA T-g, generally agree within +/-4 degrees C for a wide variety of commercially available polymers. The DMA T-g is defined as the average of E " and tan delta peak temperatures measured at a 1 rad/s oscillation frequency.