The description of the formation of spherulitic patterns is developed on the basis of assumption of randomness of the nucleation process. General relationships describing the formation of the spherulite interiors and boundaries during nonisothermal crystallization in infinite samples are derived. The method of determining the kinetics of the structure formation on the basis of the conversion degree data is proposed. The model crystallization processes are analyzed in detail : (1) an instantaneous nucleation and (2) an isokinetic crystallization. The prediction of the kinetics of spherulitic structure formation during nonisothermal crystallization of isotactic polypropylene is demonstrated and verified by the computer simulation of the polypropylene crystallization and DSC nonisothermal crystallization of isotactic polypropylene.