Criteria are discussed for using thermocouples in carbon atmospheres above 2000°C. Experimental data are given for W/Re, W/W‐25 Re, Re/W‐25 Re, graphite/Re, and graphite/Ir thermocouples in carbon atmospheres from room temperature to 2200°C. Reaction temperatures of carbon with thoria, urania, and yttria were measured to be below 1730°, 1620°, and 1590°C, respectively.