The thermomechanical and creep properties of poly(ethylene terephthalate) fibers crosslinked with 1,6hexanedisulfonyl azide, 1,3-benzenedisulfonyl azide, and 2,6-naphthalenedisulfonyl azide were investigated. Significant improvements in these properties were observed between the standard fibers and those produced by crosslinking. Cyclic loading studies highlighted minor differences not detectable by normal thermomechanical analysis. The creep at room temperature could be reduced to about one-third of the normal values observed in the untreated fiber. (C) 2003 Wiley Periodical.