The solid-state structure of syndiotactic polystyrene (s-PS) after crystallization from the melt and the glassy state was examined by differential scanning calorimetry (DSC), density, and X-ray diffraction analysis. It was possible to prepare semicrystalline s-PS containing either the pure alpha- or the pure P-crystalline form by melt crystallizing s-PS from 280 or 330degreesC. The measurements confirmed the low density of both crystalline forms, which in the case of alpha-crystalline form was smaller and in the case of beta-crystalline form was only slightly larger than the density of the glassy amorphous s-PS. An endeavor to introduce the crystalline phase in s-PS through cold crystallization at constant temperature above the glass transition resulted in a complex ordered phase. This ordered phase, depending on the crystallization temperature, contained the planar chain mesomorphic phase and the alpha-crystalline phase with a low degree of perfection (cold crystallization in the range 120-175degreesC) or a mixture of the aand beta-crystalline forms with a high degree of perfection (cold crystallization in the range 210-260degreesC). The combination of DSC and X-ray measurements enabled us to resolve the complex ordered structure in semicrystalline s-PS after cold crystallization.