Compounds in Ca-10(PO4)(6)Cl-2-Pb-10(PO4)(6)Cl-2 system were synthesized by solid state reaction. It was ascertained using DTA and X-ray diffraction methods that in the investigated system there are two fields because of the formation a compound with formula Ca7Pb3(PO4)(6)Cl-2. The first area is the Pb-10(PO4)(6)Cl-2-Ca7Pb3(PO4)(6)Cl-2 which is characterized by unbounded mixing of components. The second Ca7Pb3(PO4)(6)Cl-2-Ca-10(PO4)(6)Cl-2 area has complicated character due to presence of decomposition processes. In spite of the presence of the one nature polymorphic transitions of Ca-10(PO4)(6)Cl-2 and Pb-10(PO4)(6)Cl-2 the same effects on all solid solutions were not observed. (C) 2011 Elsevier B.V. All rights reserved.