Photografting of N-isopropylacrylamide (NIPAAm) on ethylene-vinyl alcohol copolymer films (thickness = 15, 20, and 25 mum) and low- and high-density polyethylene films (thickness = 30 mum) was carried out at 60-degrees-C in a water medium. Xanthone was used as a photoinitiator by coating it on the film samples. The resultant NIPAAm-grafted films exhibited a temperature-responsive character, which was evaluated by measuring a dimensional change of the grafted films. The grafted films swelled and shrank in water at temperatures lower and higher than around 30-degrees-C, respectively. The character was found to be reversible between 0 and 50-degrees-C. It was observed that the extent of the character is largely influenced by film thickness, location of NIPAAm-grafted chains, and crystallinity of film substrate.