Elastic properties of pure crystalline and amorphous phases of a semicrystalline polymer are usually not directly measurable by usual physical means. It therefore is necessary to resort to numerical computing methods. This paper describes some of these methods, based on atomistic simulations, as well as an assessment of current implementations, it is shown that the method proposed by Zehnder et al. (1996) gives the best results, at the expense of long computing time, due to molecular dynamic simulation. Nevertheless none of these methods are really usable on a daily basis, since there are demanding important computing capabilities.