The diffusion of nickel into undoped and silver‐doped,p‐type lead selenide crystals exhibits anomalous behavior at 700°C. The penetration profiles show pronounced minima and these minima migrate into the crystal as a function of time. The minima occur when there is aptontransition in the initiallyp‐type crystals. The diffusion of nickel inton‐type, bismuth‐doped crystals does not exhibit a minimum in the penetration profile of nickel and the crystals do not exhibit anntoptransition.