Proton conduction in the composites of heteropolyacid hydrates (Phosphotungstic acid : PTA.nH(2)O and Phosphomolybdic acid : PMA.nH(2)O) with salt hydrates like Aluminium sulphate and Ammonium paratungstate (APT) as dispersoids has been studied and compared with the composites PTA : Al2O3 and PMA : Al2O3. Thermal analysis, XRD and IR studies on acid and salt hydrates dispersed phase systems reveal the formation of composites. A significant increase in the ionic conductivity has been observed in the composites. It has been found that the conductivity of 0.5PTA + 0.5Al(2)(SO4)(3).16H(2)O is similar to1.1 x 10(-2) S.cm(-1) and that of 0.55PMA + 0.45APT is similar to1.3 x 10(-3) S.cm(-1) at 65% R.H. The temperature and humidity dependence of bulk electrical conductivity of the composites is also reported. (C) Kluwer Academic Publishers.