This system, consisting of compositions lying between the end-members, CdTe and HgTe, constitutes perhaps the third most important semiconductor after Si and GaAs. Its importance stems from the ability to tailor the band-gap precisely between that (1.5eV) of the semiconductor, CdTe, and the zero value of the semi-metal, HgTe; giving, in particular, one of the most versatile infra-red detectors known. The intermediate compositions also benefit from the usual mechanisms which improve the mechanical properties of alloys.As an aid to those working on this system, this volume summarizes known diffusion and defect properties of the end-members and of the intermediate alloys, gathered over the past few decades. The contents include data on the diffusion of Ag, Al, As, Au, Bi, Br, C, Ca, Cd, Cl, Co, Cr, Cu, Fe, Ga, H, Hg, I, In, K, Li, Mn, Na, Ni, O, P, S, Sb, Se, Sn, Te and Zn in various compositions, as well as the details of defect phenomena involving antiphase boundaries, dislocations, grain boundaries, point defects, surface defects, and twins.