A mutual inductance probe has been developed to determine interface locations between gas and liquid metal and between liquid salt and liquid metal. The probe is a bifilar coil of Nichrome wire on an alumina form contained in a Type-304 stainless-steel or ceramic wall. A high-frequency voltage supplied to one winding induces in the second winding a voltage that is related inversely to the depth of liquid surrounding the coil. Probes ≈5- and 14-in. long, were calibrated in liquid cadmium, bismuth, and sodium over a temperature range of 200 to 700°C. The device has several important advantages over other means of measuring liquid levels of corrosive fluids at high temperatures. It is compact, rugged, reliable, and reasonably accurate. For a calibrated probe, the average deviation in measured liquid level is about 3% of the length of the windings. The instrument is well adapted to operations in remotely operated facilities because it has no moving parts and can be replaced easily.