We describe the preparation of bulk and supported cesium and ammonium heteropolyacid and acid salts of 12-tungstophosphoric acid. Novel synthetic schemes to prepare supported forms of insoluble cesium- and ammonium-acid salts are discussed, and their behavior in model compound isomerization and alkylation reactions is described. In particular, we discuss the egg-white morphology associated with Cs-acid salts supported on silica extrudates prepared by a novel in situ-reaction/precipitation route. We also describe hydrothermal techniques developed for directly preparing the ammonium-acid salts of 12-tungstophosphoric acid and the extension of that technique to other heteropolyacid salts.