A solid-state method of Nafion/ceramic nanocomposite, membrane preparation was used. Nanocomposite powders from Nafion pellets and a zirconium phosphate ceramic were formed by mechanical attrition. The powders, were consolidated into membrane form by mechanical pressing. A decrease in the particle size and improved dispersion of the ceramic within the polymer phase were confirmed with scanning electron microscopy. An evaluation of membrane hydration by thermogravimetric analysis indicated that the prepared membranes had increased water Uptake in comparison with a commercially, available membrane. However, as the distribution of the ceramic was improved, the hydration of the sample Was reduced. Low-temperature differential scanning calorimetry indicated that file additional water contributed to an increase in the contents of both freezing and nonfreezing water in the membranes. proton conductivity testing at various relative humidities and temperatures revealed that the prepared membranes had conductivities comparable to but somewhat lower than those of the commercial membranes. An increase in conductivity was seen with decreased particle size and improved dispersion of the ceramic.