In connection with investigations concerning the core melt/concrete interaction, the enhancement of heat transfer between two horizontal liquid layers by gas injection has been studied using two systems—oil over water and oil over Wood’s metal—with very different density ratios. For the largest gas injection rate (superficial gas velocity 6.3×10−3 m/s), the heat transfer coefficient is increased by a factor of nearly 400 for oil over water and by a factor of ∼10 for oil over Wood’s metal In the core melt/concrete interaction, the superficial gas velocities might be even higher; therefore, the gas-induced enhancement of interfacial heat transfer should be taken into account.