Radiation-induced graft polymerization of acrylic acid (AAc) on poly(3-hydroxybutyric acid) (PHB) film was carried out and the resulting film was thermally-remolded. The PHB films grafted with AAc (PHB-g-AAc) having a degree of grafting higher than 5% completely lost the enzymatic degradability. The enzymatic degractability of the grafted film was recovered by thermal remolding. The highest enzymatic degradation rate was observed at degree of grafting of 10% after thermal remolding. The PHB-g-AAc films and thermally-remolded PHB-g-AAc films were characterized by contact angle and differential scanning calorimetry. The enzymatic degradability of PHB-g-AAc films was lost by the grafted AAc, which covered the surface of PHB film. The acceleration of enzymatic degradation in the remolded PHB-g-AAc films was mainly caused by decrease of crystallinity of PHB by dispread of grafted AAc during thermal remolding. (c) 2006 Wiley Periodicals, Inc.