Molecular mechanics calculations have been used to predict the preferred conformations of various stereochemical forms of polypropylene (PP) and polymethylmethacrylate (PMMA). The chain flexibility has been quantified by calculating the characteristic ratio (C-n) using the Monte Carlo (MC) simulation technique. It is found from the results that the total energy and chain flexibility depend on the meso-dyad ratio. The total energy corresponding to syndiotactic forms of PP and PMMA is low which suggests that PP and PMMA can be prepared in the respective stereochemical forms.