The effect of zone-drawing conditions on the structure and physical properties of PET films was examined by measuring crystallinity, birefringence and orientation of crystalline and amorphous phases. The crystallinity of the single step zone-drawn PET film increases mote rapidly with drawing temperature than it does with drawing stress. But birefringence and the orientation of the amorphous regions of the samples increase more rapidly with drawing stress than they do with drawing temperature. At lower zone-drawing temperatures. the amorphous phase contribution to the total birefringence is higher than the crystalline phase contribution. At higher zone-drawing temperatures, on the contrary. the crystalline phase contribution to the total birefringence is higher than the amorphous phase contribution.