The pyhsical properties, which are important for the textile use, of the PET polyester fibres produced in Turky were investigated. Thy were namely the elastic properties like tensile strength, elongation at break, tensile, bending and torsional moduli, and the properties related to the inner structure such as density, melting point, viscosity, birefringence and c ystallinity. Samples of PET - polyester fibres from POY and flat (straight filament) yarns of six main producers of Turkeu were used for determinations. The dearee of mlstdlinitv was eskmated on the basis of thedens[- tyd measu;ements. It was found that the main physical properties of the polyester fibres from POY and flat yarns produced in Turkey were smilar to those produced elsewhere except that slightly lower young modulus and crystallinity in both POY and flat yarns were found.