In this study, the erosion of poly(tetrafluoroethylene) TFE Teflon by hyperthermal atomic oxygen (AO) has been examined using X-ray photoelectron spectroscopy (XPS). The initial F/C atom ratio of 1.66 decreases to 1.15 after a 2 h exposure to a flux of 2 x 10(15) atoms/cm(2) s AO with an average kinetic energy similar to5 eV. The F/C atom ratio is further reduced to a value of 0.90 after a 25 h exposure. The high-resolution XPS C Is data indicate that new chemical states of carbon form as the F is removed, and that the relative amounts of these states defend on the F content of the near-surface region. The states are most likely due to C bonded only to one F atom and C bonded only to other C atoms. Exposures of the AO-damaged surface to research-grade O-2 results in chemisorption of a very small amount of O (similar to0.8 at. %); this indicates that large quantities of reactive sites are not formed during the chemical erosion by AO. Further exposure to AO removes this chemisorbed oxygen. After exposing the AO-exposed surface to air for 90 min, O-2 is chemisorbed and the F/C atom ratio is reduced to 0.68. Another 46 h of AO exposure results in removal of this O and a further decrease in the F/C atom ratio to 0.58.