The aging of the binders GAP-N100 and HTPB-IPDI was investigated by DMA in torsion mode to find out the changes in the storage shear modulus G＇(omega), loss shear modulus G"(omega) and in the glass transition temperature TG The forced sinusodial deformation method was used with measuring frequencies between 0.1 Hz and 56.2 Hz. A measurement temperature range between -100 degrees C and +50 degrees C was applied. The DMA instrument was a Rheometrics Dynamical Spectrometer, type RDS II/7700. Non-aged GAP-N100 shows a well defined steep glass transition between -40 degrees C and -25 degrees C, which is found with aged samples also but shifted to higher temperatures. The glass transition of the binder HTPB-IPDI lies between -70 degrees C and -10 degrees C, but HTPB-IPDI has not a well defined glass transition. With aging it looses its glass transition, which can be seen by a smoothing out of the transition step in the curve G＇(omega) = f(T). The Behaviour and the differences of these binders are explainable on a molecular basis. The systematic shift of the glass transition temperature of the non-aged and aged GAP-N100 as well as of the non-aged HTPB-IPDI is describable by the Williams-Landel-Fery equation. This equation was used to extrapolate the values of the glass transition temperatures to shear rates possible during operational use of propellants.