Highly regioregular isotactic polypropylene samples containing only rr defects of stereoregularity in a wide range of concentration have been obtained with a series of regiospecific metallocene catalysts. A study of the relationships between kinetics of melt-crystallization and the microstructure of polypropylene chains is reported. The equilibrium melting temperatures for isotactic polypropylenes of different stereoregularity have been estimated. The kinetic study has shown that the crystallization rate increases with increasing the concentration of rr defects and decreasing the molecular weight. During isothermal crystallizations from the melt, crystals of a form develop at the beginning of the crystallization, whereas the formation of crystals of gamma form is observed only at longer crystallization times. According to the literature, the crystals of gamma form are nucleated over the preformed crystals of a form.