The results of a study of probabilistic distributions of hardness in H-bands of steels 30KhM and 20KhGNM are presented. The coefficients of regression and correlation between the hardness and the content of the alloying components are obtained for various distances from the ends of the quenched specimens. The study has been performed by the method of computer statistical processing of the density of distribution of the hardenability curves in H-bands of the steels. The results are shown to be applicable for predicting the correspondence between the hardness in critical cross sections of steel parts and the specified requirements.