Thermal conductivity of Acheson graphite is reported for the temperature range −150°C to +700°C. Cylindrical blocks of the material were placed above and below a flat electric heater and lateral losses balanced out by auxiliary coils wound on the surface of the sample. The results show a continual decrease in thermal conductivity with temperature over the entire range. The law,k/aC=A/T+B,proposed by Bidwell for certain other materials is found to hold accurately for graphite.