Inorganic-organic composite electrolytes for use in dry fuel cells were synthesized from CsHSO4 (CHS) and 1,2,4-triazole (Tz). CHS and Tz were mechanochemically treated in a dry nitrogen atmosphere to obtain composites with xCHS.(100 - x)Tz, where x is the amount (mol) and was varied in increments of 10 between 90 and 50. Structural investigation of the composites indicated that chemical interactions occurred between CHS and Tz after solid-state mechanochemical treatment. The proton conductivity of the composite electrolytes was largely increased by introduction of Tz, particularly in the low temperature region. The composite with x = 80 showed high proton conductivity (6.0 x 10(-4) to 1.60 x 10(-3) S cm(-1)) over a wide temperature range (60-160 degrees C) in a dry atmosphere. These observations suggest that proton transfer in the CHS and Tz composite systems includes the proton-hopping mechanism and self-dissociation. This phenomenon probably supports proton diffusion, especially in low temperature regions. (C) 2010 Elsevier Ltd. All rights reserved.