The quasi-ternary Cu2Se-CdSe-In2Se3 system was studied by differential thermal analysis (DTA), X-ray diffraction, and metallography. The phase diagrams of eight vertical sections, the isothermal section at 820 K and the liquidus surface projection were constructed. The liquidus consists of 11 fields of primary crystallization that are divided by 23 monovariant lines and 23 invariant points. The type and temperatures of the monovariant and invariant processes were determined. Two quaternary compounds, CuCd2InSe4 and CuCdIn10Se16.5, which melt congruently at 1283 and similar to 1123 K, respectively, form in the system. CuCd2InSe4 crystallizes in the sphalerite structure and has a homogeneity region, which is localized along the quasi-binary CuInSe2-CdSe section. (C) 2003 Elsevier B.V. All rights reserved.