This paper reports experiments on the influence of the post-thermal treatment temperature of the polyimide (PI) film on laser-induced periodic surface structures (LIPSS). PI films were thermally treated at different temperatures ranging from 100 to 270 degreesC. The degree of imidization, the glass transition temperature and the surface roughness of polyimide films increased with the increase of the thermal treatment temperature. LIPSS were obtained on PI films under the irradiation of a linearly polarized UV laser with a wavelength of 355 nm. The formation process and the configuration of LIPSS varied with thermal treatment temperature. The formation of LIPSS consisted of an incubation stage, a rapidly developing stage and a stable stage. The incubation stage prolonged when the sample was treated at a higher temperature. The periodicity of the ripples on films treated at a temperature above 150 degreesC displayed an obvious decrease as the laser fluence increased. (C) 2002 Elsevier Science B.V. All rights reserved.