Conductivities of nitrate composites (1 - x)MeNO(3)-xAl(2)O(3), where M = Li, Na and K, were investigated in comparison with conductivities of the individual salts. The composites were prepared by mechanical treatment in planetary mills followed by sintering. Conductivity isotherms exhibit maxima at x = 0.40-0.60, with the conductivity values around 10(-2) S/cm at 500 K, these are 10(3)-10(5) times higher than those of the pure salt. Temperature dependences of conductivity are not linear in Arrhenius coordinates. A possible reason for the drastic change of transport properties of nitrates in composites under study may be the stabilization of amorphous high-conducting phases of nitrates which are formed on MeNO(3)-Al2O3 contacts as a result of the interface interaction between the components.