Plasma treatment of PET films was carried out under argon, followed by exposure to an oxygen atmosphere. The films underwent considerable changes in surface composition and morphology, as demonstrated by contact angle measurements, FTIR-ATR, AFM, and XPS. It was found that the surface acquired oxygen containing polar functional groups such as -C=O, -OH, and -OOH, which increased in number as the plasma treatment time increased. During storage, the treated films underwent significant surface reorganization, and both the time and temperature contributed to the increase in the contact angle. As revealed by AFM measurements, these changes were accompanied by an increase in roughness in the form of ridges. The ridges were observed to grow in height with increasing treatment time, although their spacing showed little evolution. A correlation among the observations obtained from various techniques was established, giving a comprehensive picture of the structure and dynamics of plasma-treated PET surfaces. (C) 2000 John Wiley & Sons, Inc.