The interactions between both cleaved and ion-sputtered (HgCd)Te and deposited overlayers are reviewed. The overlayers are classified into four groups—ultrareactive, reactive, intermediate reactive, and unreactive—based on the relative heats of formation of the overlayer telluride and HgTe and CdTe. Ultrareactive overlayers react with both HgTe and CdTe to form an interfacial metallic telluride and elemental Hg and Cd (which are lost from the interface), while reactive overlayers react only with the HgTe component. Once the HgTe is depleted from the surface region, further deposition results in growth of a metallic film. Unreactive metals, on the other hand, do not react with the surface, but form a stoichiometric interface. Finally, the extent of interactions between intermediate overlayers and(HgCd)Te depend on other factors, including the stability or reactivity of the surface and substrate material, the heats of cation alloying, and the propensity of the overlayer element to diffuse into (HgCd)Te.