A technique is described which allows the measurement of the thermal conductivity &kgr; of superconductors belowTcwithout the use of a thermometer, ifTcis known. The method is particularly adapted to technical superconductors of poor thermal conductivity. It is convenient to use as sample a superconducting wire or band provided with a high conductivity matrix of a normal metal, which has to be removed from the test length. The stabilized ends of the sample are thermally anchored to a heat sink of variable temperatureT. A currentIflowing through the conductor holds the middle part of the test length in the normal state due to Joule heating. The length of the normal section and hence the voltage appearing on the sample are a functions ofIandF&kgr;dT. The variation of the temperature of the heat sink then allows the determination of &kgr; (T). Results for two NbTi samples are included.