Silk fibroin cast film was prepared using a ternary solvent system of CaCl2/CH3CH2OH/H2O (1/2/8 in mole ratio). A drying temperature at casting influenced crysta1 structure of fibroin. When a drying temperature was set at 4 centigrade, the cast film became amorphous. When a drying temperature was set higher than 60 centigrade, a fibroin film of silk-II crystal was obtained. A fibroin film of silk-I crystal was obtained in the temperature range from 10 to 50 centigrade. Also, silk-I crystal was generated from random coil through exposure of an amorphous film to water vapor at 20 centigrade. As for the crysta1 transformation from silk-I into silk-II, the treatment with a glycerol solution was effective. In the course of the treatment a film showed self-thinning and self-expanding. The expansion ratio exceeded 30 % at maximum. The film produced accompanying self-expansion was ductile in nature. L929 cells were cultivated in MEMAM containing extracts from silk fibroin films. The extracts did not inhibit the multiplication of L929 cells.