A solid state method of Nafion (R)/ceramic nanocomposite membrane preparation is described. A nanocomposite powder from Nafion pellets and a zirconium phosphate ceramic is formed by mechanical milling. The nanoparticles are then consolidated into membrane form by mechanical pressing. Cross-sectional analysis by scanning electron microscopy indicates that the ceramic particles exist in agglomerates that are evenly dispersed across the membrane. Dynamic mechanical analysis and tensile testing found the membranes to be mechanically equivalent, and in some cases Superior, to a commercial extruded membrane. Increasing ceramic content is accompanied by an increase in modulus and shift in the alpha peak to higher temperature. Maximum water uptake of the membranes, as measured by thermal gravimetric analysis, is double that of values reported for the commercial membrane, and complete dehydration is postponed to higher temperature. The proton conductivity Of fully hydrated membranes, measured by the 4-probe method at 60 degrees C in water, is comparable with that of the extruded membrane. (C) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 111: 1144-1150, 2009