The effect of adding a polyanionic saccharide (alginic acid, pectic acid, agarose, kappa-carragenan or lambda-carragenan) to a collagen solution on the reconstruction rate of collagen molecular assembly was evaluated. The rate of collagen molecular assembly was reduced by the addition of alginic acid and of pectic acid that was containing carboxy groups. Dextran, agarose, and soluble starch did not affect the rate, while dextran sulfate and lambda-carragenan accelerated the rate of collagen molecular assembly. The denaturation curves of collagen reconstructed with lambda-carragenan showed two peaks at about 45 degrees C and 55 degrees C. The use of a polyanionic saccharide made it possible to endow the reconstructed collagen fibrils with flexibility to enhance the application of collagen as a scaffold material for tissue engineering.