An investigation of the temperature and slag regimes of concrete linings has shown that one half of the lining's thickness, the one on the metal melt side, is subjected to severe cyclical changes in temperature, whereas the other half operates under steady thermal conditions throughout the furnace campaign. It has been established that cooling of the lining with water sharply reduces the temperature of the contact layer of the lining, i. e., it leads to thermal shock with accompanying crack formation. The durability of the lining is largely determined by the correspondence of the chemical nature of the lining material with the chemical composition of the slags. Under the influence of converter slag with a basicity of 3,1–4.5, the rate of transfer of SiO2 from the acid lining to the slag increases by 2–3 times in comparison that observed for slag with a basicity of 2.5–3.35. This in tarn leads to more intense decrease in the basicity of the ladle slag, enhancing its fluidity and causing intense wear of the lining in the lower sector of the ladle. The results of industrial tests showed that the most agressive effect on an acid lining is exerted by fluid slags with a basicity of 2.1–2.7. Slags of lower basicity are more viscous and closer in chemical composition to that of the lining. Slags of higher basicity have a higher viscosity and their penetrative power is therefore less.