Iron and sulphur are the main components of many metallurgical semiproducts. For this reason phase diagrams of multicomponent systems formed on the basis of binary Fe-S system are very important for the extractive metallurgy of nonferrous metals. On the other side, thermodynamic databases for melts and alloys with sulphur are characterised by the lack of information due to different methodological difficulties of experimental research with such volatile and aggressive element, as sulphur. These factors became the main reason for providing the detailed research of phase high-temperature equilibria in the ternary Fe-S-X (X=Co, Cu, Ni, Sn) systems with the use of experimental methods. The presented work was performed with the use of thermal methods (TGA, DSC, and STA), scanning microscopy methods (SEM/EDX) as well as XRD analysis. Desired compositions of listed systems were limited by pseudobinary sections of congruently melted sulphides, namely, Fe1-xS – Ni1-xS, Fe1-xS – Cu2±xS, Fe1-xS – Co1-xS and Fe1-xS – Sn1-xS. Phase diagrams of these sections also have been constructed. It was shown, that sulphides of nickel and iron, as well as sulphides of iron and cobalt are formed the continuous solid solutions within the whole composition range at high-temperature region. Besides, sulphides of iron and copper both sulphides of iron and tin have the eutectic reaction at the wide composition area, as well as limited solid solutions. After construction and critical assessment of phase diagrams for all boundary binary systems the research was focused on high-temperature phase equilibria, realised in ternary Fe-S-X (X=Co, Cu, Ni, Sn) systems. More than 80 samples for each system were prepared in laboratory conditions for further experiments. All samples were investigated by thermal analysis with the use of high-temperature modular platform Setsys evo, manufactured by SETARAM Instrumentation Company. Received results gave us information about types and temperatures of phase reactions during the heating in the wide temperature ranges. Also it should be noted about interesting and safe experimental technique, which is proposed by us for investigation of systems with volatile and aggressive elements under providing of thermoanalytical experiments. Chosen compositions were additionally examined with the use of SEM/EDX and EPMA methods. Obtained data about compositions and structures of coexisting phases gave us the relevant information for determination the tie-lines, monovariant lines and nonvariant points of phase reactions. The main results of research are the liquidus and solidus surface projections for ternary Fe-S-X (X=Co, Cu, Ni, Sn) systems, which will be presented during the conference.