This study has revealed the advantages of synchrotron radiation X-ray fluorescence analysis (SR-XRF) utilizing 12 keV X-rays concentrated with polycapillary x-ray optics for nondestructive discrimination of polyester white single fibers. Twenty kinds of polyester white single fibers collected from 11 automobile trunk mats and 9 clothes were used as analysis samples. Titanium derived from TiO<sub>2</sub> delustering agents, Ca derived from CaCO<sub>3</sub> fillers, Sb and Ge derived from polymerization catalysts, elements such as Mn, Co, Ni and Cu derived from transesterification catalysts could be detected from polyester white single fibers. The elements detected can be used as important indexes to characterize the samples. In order to discriminate single fibers for clothes in which Ti and Sb were only detected, it has been suggested that comparison of x-ray intensity ratios of Sb Lα,β/Ti Kβ is effective. This technique should provide an effective approach to nondestructive discrimination of polyester white single fibers.<br>