As a phase-change material (PCM) for high-temperature heat storage at around 80-90degreesC, D-threitol, which is an isomer of meso-erythritol, was studied to obtain its phase-change characteristics by means of DSC and a lab-scale heating and cooling apparatus. It was found that D-threitol started to melt at around 90degreesC with a relatively large latent heat of 225 kJ/kg. Upon cooling, D-threitol started to solidify at around 40-46degreesC and its temperature rose rapidly to 89degreesC. From these results it was considered that D-threitol is applicable as an environmentally friendly PCM for high-temperature heat storage for hot water supply.