The effect of talc as an artificial nucleating agent in different concentrations on the crystallization of polypropylene (PP) has been studied. It is considered that the induction time should be taken into account in the Avrami evaluation of isothermal crystallization. From a study of nucleated PP samples prepared in different ways, it has been proved that the nucleating effect of talc slightly decreases with increasing time spent by the sample in the state of the polymer melt. It has been shown that crystallization of non-nucleated polypropylene strongly depends on the material of the sample pan. It has been established that dilatometry cannot be used to study the isothermal crystallization of nucleated polypropylene, since microcracks appear in the sample, partly compensating the volume decrease due to the crystallization process.