The measurements were made in a torsional pendulum at about 0.1 cps using bongitudinal stress (5 - 150 MPa) in the temperature range 20 - 600°C. The internal friction (i.f.) decreases and the modu- lus increases monotonously with increasing longitudinal stress in the, amorphous state. This i.f. change is more pronounced in the temperature range of structural relaxation. Changing the stress at constant temper- ature the changesof the measured parameters were time andtemperature dependent. These effects can be explained by the diffusion controlled reversible ordering of the atoms due to the applied stress. Also the isothermal crystallization was accelerated by the stress.