Abstract: A process and apparatus for controlling the level of a molten metal surface in a continuous casting mould uses a probe located either in the molten or above the surface of the molten metal. The probe is connected to a high-frequency transmitter which is arranged to induce voltages in each of two secondary receiver-coils, the receiver-coils being in coupling relationship with a compensating coil and a further coil connected to the probe. The receiver-coils are connected in opposition to one another so that a difference voltage of zero is arranged to be produced when the molten metal surface is at the required level but that the difference voltage is used, when departing from zero, for control purposes of the height of the molten metal surface.