Simultaneous small angle X-ray scattering, wide angle X-ray scattering and differential scanning calorimetry have been used to study the effects of sub-zero temperatures on the structure of hydrated starch granules. Results indicate that completely reversible compression of the starch lamellar structure occurs upon the freezing of water and ice formation. It is proposed that this compression, caused by the expansion of water upon freezing, results in preferential compression of the more 'open' amorphous lamellae which act as 'shock absorbers'. The lamellar repeat distance is reduced whilst periodicity is maintained. For solvents other than water, which do not expand on freezing, the behaviour is qualitatively different since no compression occurs. Freezing behaviour-as well as providing information about the micromechanical properties of starch granules-also has implications for cryo-microscopy studies of starch.