The phase diagram of the GeSe2-PbTe system is studied by means of X-ray diffraction, differential thermal analysis and measurements of the microhardness and the density of the material. The unit-cell parameters of the intermediate phase alpha-GeSe2.(2-x)PbTe, (x = 0/1) were determined: a = 6.200 angstrom, b = 3.807 angstrom, and c = 3.645 angstrom, alpha = 106.47 degrees, gamma = 99.85 degrees, and gamma = 87.22 degrees. The intermediate phase alpha-(GeSe2PbTe)-Pb-. receives a peritectic reaction at 425 degrees C. This phase has variable composition GeSe2(2 - x)PbTe (x = 0/1), it melts congruently at 425 degrees C and stands polymorphic transition at T-alpha <->beta = 325 degrees C, which dependents of the composition (x). The existence of a narrow regions of solid solutions based on PbTe is supposed. (c) 2007 Elsevier B.V. All rights reserved.