For structural steels, correlation between the value of minimal brittle fracture stress within the ductile-to-brittle-transition temperature range (brittle strength $R_{MC}$) and yield strength is ascertained over the wide range of strength variation. As shown, the characteristics of this correlation are changed at transition from ferrite—pearlite structure to the structure of tempered martensite, i.e., they are structurally sensitive. Physical interpretation of these results is presented. The obtained results enable to predict the brittle strength of steel without the need for expensive and time-consuming low-temperature mechanical tests.