The diffusion behavior of mercury in Hg0.8Cd0.2Te was investigated using radiotracer techniques. Complex concentration versus distance profiles resulted from both the gold and mercury diffusion anneals. At 225 °C, complementary error function curve fits to the surface and tail components of the mercury diffusion profile yielded diffusion coefficients of ≂8×10−14and ≂2.5×10−11cm2s−1for the surface and tail regions, respectively. Mercury diffusion coefficients were similar for as‐grown and mercury preannealed samples. Surface concentrations were unknown for the gold diffusion profiles and accurate diffusion coefficient calculations were not made, but the migration rate of gold appeared faster than mercury in Hg0.8Cd0.2Te. A mechanism was proposed for depletion of gold in the near‐surface region of the HgCdTe for long diffusion times in a mercury ambient, which involved the formation of Au/Hg compounds at the slice surface.