Used X-ray and lith films are composed of a protective layer, a gelatin layer (photosensitive layer) that contains silver particles, and a base poly(ethylene terephthalate) (PET) layer. In stainless steel tube reactor, used films were immersed in water and gelatin in both protective layer and gelatin layer was hydrolyzed under subcritical condition. After reaction for 5 min at 175 degrees C, the entire amount of gelatin was decomposed, and the PET film and silver particles were recovered independently. In the case of the lith film, incubation at 200 degrees C for at least 5 min was required for the complete decomposition of gelatin. Gel permeation chromatography (GPC) analysis of the water- soluble reaction mixture indicated that the average molecular mass of water- soluble gelatin decreased over time.