In order to predict polymer durability during long term exposure to aggressive environments, it is necessary to study the effects of solvent-induced crystallinity. In this study, poly (ether ether ketone) (PEEK) powder was compression molded into amorphous films. One amorphous film was thermally crystallized. Both amorphous and thermally crystallized films were exposed to acetone at room temperature and 45 deg. C. Periodic absorption measurements were made. Wide angle x-ray diffraction and differential scanning calorimetry data indicated that solvent-induced crystallinity was present in the samples exposed to acetone at both temperatures.