The method of determining the thermal conductivity of a metal with this apparatus consists, essentially, of measuring both the axial temperature gradient and the transfer of heat under steady state conditions in a thermally shielded cylindrical rod of the metal which is heated at one end and cooled at the other. The objective was to make precise determinations of conductivity without reliance on previously established data for standard metals. In certain respects the apparatus embodies simplification of, and improvement over, other equipment of this type. A calorimetric measurement of heat flow constitutes a distinct advantage of the instrument both as to its simplicity and the fact that it supplies the data necessary for a direct rather than a comparative evaluation of thermal conductivity. Other features include vacuum operation and special instrumentation to facilitate the measurement of temperature differences. Tests have been made on nickel, zirconium, and a zirconium‐3‐percent‐tin alloy from room temperature up to the range between 500 and 700°C. Where comparison is possible the results are in close agreement with some of the most accurate published data of this type.