Communication: The influence of the concentration of poloxamer 407, the pH and the temperature on the gelation of silk fibroin (SF) were studied. It was found that the gelation of SF occurred in the presence of poloxamer at pH value of 7.0 while gelation of SF itself did not occur. The gelation time of SF was shortened with increasing the poloxamer. From infrared (IR) and circular-dichroism (CD) spectroscopy measurements, it was found that a conformational change of the SF in the SF/poloxamer system from random coil to beta-structure was accelerated after forming a polymer complex with the poloxamer. The crystallinity of the poloxamer was reduced by SF from X-ray diffraction measurements.