Abstract Optical rotatory power, viscosity and osmotic pressure of dilute aqueous solutions of amylose have been studied. Optical rotatory dispersions of amylose and β -limit dextrin in 0.2 m potassium chloride and 0.5 m potassium hydroxide are normal and can be well expressed by a single term Drude equation. All of the λc obtained from the analysis of the dispersion curves are close to 140 mμ which may be considered as a characteristic value of glucopyranose residue. This seems to indicate that there is no well-oriented helix of amylose in the solutions. With increasing temperature, the optical rotations of amylose and β-limit dextrin decrease. Amylose, especially in a neutral aqueous solution, has an unusually great temperature coefficient of specific rotation amounting to −1.4°/°C a the largest value. Parallel with this change, the viscosities of the amylose solutions decrease with increasing temperature. These results seem to be well explained by assuming that the flexibility of amylose molecules is considerably influenced by temperature through the change of the degree of hydrogen bonding between segments of the molecules. Osmotic measurements have given evidence to prove the occurrance of the association of amylose molecules in the solution examined. The degree of the association has been found to decrease with increasing temperature. These facts indicate that hydrogen bonding plays a significant role in the properties of the dilute aqueous solution. The molecular configuration of amylose in aqueous solutions has been discussed. It seems to be most probable that amylose molecules in the solutions take the configuration of deformed helix, and associate highly with each other. No linear extended configuration is possible. The figure of the supposed configuration is drawn.