To determine thermal conductivity of dentin, an apparatus designed to measure the thermal conductivity of small samples was constructed. The apparatus consists of 2 copper rods (thermodes), the same diam. as the specimens, mounted with spring tension for alignment and contact. One of the thermodes serves to introduce heat into the system and the other to remove heat. Thermocouples were placed at one-centimeter intervals along the thermodes. Temperature readings from the thermocouples permitted calculation of the amount of heat flowing through the thermodes and sample. With this apparatus the thermal conductivity of human dentin was found to be 2.29 x 10-3.