The crystal structure of the ordered a form of syndiotactic polystyrene and the adjacent reentry folds of the polymer chains have been analyzed by molecular mechanics adopting various set of potential functions. The energy calculations indicate that the crystal structure is well described by the P3 space group, in accordance with the experimental crystal structure recently reported. The energy required to fold the polymer chains has been optimized by taking into account both the conformational energy of the folds and the interactions between the atoms of the folds and the atoms of the crystal. The work of fold evaluated for the cc form is very similar to that previously calculated for the form, suggesting that the chain folding of syndiotactic polystyrene is regulated by the conformation and configuration of the chains rather than by their modes of packing.