A 0.3 mm thick amorphous poly(ether ether ketone) (PEEK) film was exposed to acetone until equilibrium in the weight uptake was recorded, and was then dried in a vacuum oven at 70 degrees C. The resulting structure was compared to the initial structure by means of differential scanning calorimetry (d.s.c.), wide-angle X-ray scattering (WAXS), small-angle X-ray scattering (SAXS), and infra-red (i.r.) spectroscopy. Although the exposed film remained translucent, all of these complementary techniques suggested the presence of crystallinity which was induced by the exposure of the amorphous PEEK film to the solvent.