It is shown that in a cryostat the use of an isothermal path leading out of an applied magnetic field will ensure insensitivity of thermocouples to the magnetic field. Tests in liquid helium in such a cryostat were conducted on a number of thermocouples with the applied field ranging up to 100 kG. The results showed that Cu‐constantan, Cu&sngbnd;Au 0.03 at.% Fe, and Cu&sngbnd;Au 2.1 at.% Co thermocouples are not affected by magnetic fields. In subsequent work up to 300 K the first two thermocouples listed were still insensitive to magnetic fields. The third thermocouple was not tested at the higher temperatures.