An inductively heated graphite furnace having a ⅜‐in.‐diam source of blackbody radiation for pyrometer calibration is described. The furnace is fabricated from simple, easily demountable parts and may be operated at 1800°K for 6 h with only infrequent attention; temperatures to 3000°K may be obtained for shorter periods. Source temperatures are stable and are rapidly attained. The time constant is approximately 2½ min. Special atmospheres are not required for furnace operation since graphite oxidation is minimized through furnace design.