Wax (predominantly tricosane paraffin wax, with a melting temperature of ) filled with hexagonal boron nitride (BN) particles was found to be an effective phase-change thermal interface material. The thermal contact conductance, as measured with the interface material between copper surfaces, decreased with increasing temperature from , but increased with increasing temperature from . The melting of the wax enhanced the conductance, due to increased conformability to the mating surfaces. For a given BN volume fraction and a given temperature, the thermal contact conductance increased with increasing contact pressure. However, a pressure above resulted in no significant increase in the conductance. The conductance increased with BN content up to , but decreased upon further increase to . The highest conductance above the melting temperature was , as attained for a BN content of at and . Below the melting temperature, the highest conductance was , as attained for a BN content of at and .