Ore forming conditions for Au-Sb and Ag-Sb deposits have been estimated using thermodynamic modeling. PTX-parameters of ore-forming fluids obtained by fluid inclusion study in the minerals were used as original data for modeling. Analysis of composition of fluid inclusion solutions in the minerals of Au-Sb deposits together with mineralogical and geochemical data show that Au-Sb deposits were formed by two types of solutions: neutral-weak alkaline (C-Cl < 5 wt % NaCI-eq.), and acid high concentrated chloride solution (up to 30 wt% NaCI-eq.), containing FeCl2 and CaCl2 besides NaCl. In low concentrated chloride solution Sb is transported as sulfide and hydroxide complexes, and Au and Ag as bihydrosulfide species. In acid high chloride solution of late superimposed stage, which contains Cu, Ag, Pb, and Zn, predominating Au and Ag species are chloride complexes, and for Sb chloride and hydroxy-complexes. The main factors determining geochemical specialization of Ag-Sb ore are high chloride concentration and pH = 3.5-4, determining low Au-bearing capacity of the solution. Unsaturated in Ag low concentrated chloride solutions took part in Au-Sb deposit forming that determines their specific composition. (c) 2006 Springer Science + Business Media, Inc.