The thermal diffusivities of (Hg1−xCdx)1−yTey and (Hg1−xZnx)1−yTeywith 0.55 ≤ y ≤ 1.0 and 0.0125 ≤ x ≤ 0.05465 and of pure Te are measured over a wide temperature range by the laser flash technique. The diffusivity of near pseudobinary Hg1−xCdxTe solids decrease more rapidly with temperature approaching the melting point than pseudobinary solids previously reported. The solid diffusivity for x=0.02817 is 0.83 mm2/s at 371°C, decreasing to 0.22 mm2/s at 614°C. The diffusivity of Te rich (Hg1−xCdx)1−yTey melt increases with x and with temperature. The melt diffusivity for x=0.03934 is 0.91 mm2/s at 485°C, increasing to 4.93 mm2/s at 851°C. For Te rich (Hg1−xZnx)1−yTey melt with x=0.0125 and y=0.7944 there appears to be a minimum diffusivity of about 2.6 mm2/s near 700°C. The thermal diffusivity of pure Te solid is 0.97 mm2/s at 300°C and decreases to 0.64 mm2/s at 439°C. The melt diffusivity is 1.52 mm2/s at 486°C, increasing to 3.48 mm2/s at 584°C.