Silk fibroin (SF) thin film was prepared via colloid chemical routes (CC) and by pulsed laser deposition (PLD). Secondary structure of the CC film, as examined by FT-IR, was random coil. By a post treatment with methanol, it transforms to beta-sheet. As for PLD films, the beta-sheet structure of SF powder was mostly preserved as deposited. This suggests that the post treatment is effective to restore the original P-sheet structure in the thin films. Transformation from random coil to beta-sheet is easier in the film on the substrate of polyethylene than Si(1 0 0) due to weaker affinity to silk fibroin. (c) 2004 Published by Elsevier B.V.