The thermal diffusivity of Hg1−xCdxTe melts is found to rise rapidly with temperature to values characteristic of metals. Solid and melt diffusivities for values ofxfrom 0 to 0.3 and over a temperature range from 150 to 900 °C have been determined by the laser flash method of Parker, Taylor, and Cowan. The diffusivity decreases from a maximum atx=0 in both the solid and the liquid, with the values observed atx=0.3 being about 40% of those forx=0. The solid diffusivity forx=0 is 1.7 mm2/s at 150 °C, decreasing to 0.7 mm2/s at the melting point. Thex=0 liquid diffusivity increases from 0.7 mm2/s at the melting point to 3.5 mm2/s at 900 °C.