The article presents the results of the investigation of infl uence of the boundary conditions heterogeneity on the rate of cooling of the metal during the continuous casting of cylindrical billets of highquality steel grades. It was assumed that the boundary conditions are not uniform along the length of the billet. The authors have made the comparative analysis of temperature gradients and thermal stresses occurring in solidifying billet at diff erent cooling modes implemented in the secondary cooling zone. The conclusions about the impact of the cooling intensity on the quality of the cylindrical cast billets were obtained on the basis of these results. The article also provides recommendations on the organization of rational heating modes of casting of cylindrical cast billets.