Conductivity, structure and thermodynamic parameters of CsCl in (1 - x)CsCl-xAl(2)O(3) composites are investigated. As the heterogeneous dopant, highly-dispersed alumina with specific surface area 210 m(2)/g is used. Maximum conductivity 9 x 10(-4) S/cm at 400 degreesC occurs at x = 0.6. As x rises, conductivities of bcc and fee phases tend to level off and at x > 0.6 no conductivity drop due to the phase transition occurs. The phase transition enthalpy decreases with x and at x > 0.6 no bcc-fce phase transition is detected by DSC technique. New peaks attributed to fcc-phase with the lattice parameter a = 0.694 nm are observed on X-ray powder diffractograms. At high x conductivity enhancement is likely to be due to the presence of the high-temperature fcc phase of CsCl stabilized on CsCl-Al2O3 interfaces.