Abstract Thermomechanical and dynamic mechanical measurements were made on some common amorphous polymers which had been deformed in uniaxial tension below their glass transition temperatures ( T g). Stress-temperature experiments showed that a stress increase began just above the draw temperature for constrained samples which had been uniaxially predrawn. Similarly, unconstrained samples heated above the deformation temperature shrank in the draw direction. Dynamic mechanical experiments demonstrated the appearance of a relaxation below T g which disappeared upon annealing for the drawn samples. This behaviour was attributed to a partial release of energy stored during deformation. A qualitative explanation of the energy storage mechanism is proposed.