The structure of freeze-dried atactic polystyrene (a-PS) prepared from dilute benzene and cyclohexane solutions was examined by using Fourier transform infra-red spectroscopy, wide-angle X-ray scattering and differential scanning calorimetry (d.s.c.). The phenyl-phenyl correlation in the freeze-dried a-PS is weak compared with that in the reference sample cast from a 5 wt% solution in tetrahydrofuran. The data suggest an expanded chain conformation for the specific structure of freeze-dried a-PS, which can easily be formed from a good solvent at high temperature, and with high-molecular-weight a-PS. The d.s.c. data of freeze-dried a-PS showed an endothermic peak just below the glass transition temperature, indicating an enthalpy difference between the freeze-dried and melt states.