Commercially available regular denier poly(ethylene terephthalate) (PET) fabrics were used in this investigation. PET fabric samples were wound on a bobbin and then exposed to supercritical CO2 under conditions representing a typical supercritical CO2 dyeing cycle. Infrared spectroscopy, X-ray diffraction, differential scanning calorimetry, and scanning electron microscopy were used to characterize the chemical and morphological changes of the PET fibers. The results showed that exposure to supercritical CO2 did not cause chemical changes in the fibers; the crystal size and the T-mp of the PET fabric after treatment in supercritical CO2 did not significantly change; the crystallinity decreased; and the treatment in supercritical CO2 at higher temperature caused surface morphology changes (increased oligomer migration). However, there was no pitting, cracking, or crazing on the surface of the treated fibers. (C) 2004 Wiley Periodicals, Inc.