It is known that crystallization of polymers occurs in two steps. Firstly spherulites composed of thick lamellar crystals grow and secondly thermally less stable crystals appear in the amorphous region surrounding the thick lamella crystals. The first and second steps are called primary and secondary crystallization, respectively. In this study attention was paid to the secondary crystallization process and melting of the less stable crystals. The heat capacity and the small and wide angle X-ray scattering have been measured simultaneously. It was found that the crystals generated in the secondary crystallization took long time to complete melting.