Abstract Vapour pressure measurement in the Cd–Zn–Te system is reported for T=700–1300 K and P≤760 mm Hg. From the experimental data for x=0.05, 0.10, 0.15, 0.25, 0.5, 0.75, 0.80, 0.90 and 1.0, complete P–T projection of the phase diagram for the quasi-binary Cd1−xZnxTe system has been constructed. Transformation of the P–T projection was traced for the whole range of the Cd1−xZnxTe solid solution as a function of the ZnTe concentration. From detailed studies of sections x=0.05, 0.1, 0.15 and 1.0, maximum non-stoichiometry as a function of temperature was determined both for Te and metal solubility. For ZnTe the solidus volume is on the Te side of the stoichiometric plane (50 at.% Te). Zn-boundary of ZnTe solidus is 50.004–50.005 at.% Te in composition at 826–1153 K. Formation of the Cd1−xZnxTe solid solution leads to extension of the homogeneity range, especially at high temperatures. Increase of ZnTe content in the solid solution results in a shift of the solidus toward Te, so that already for x=0.15 the solidus does not contain the stoichiometric plane.