This paper presents the results of new investigations into the preparation, stability, conductivity, and structure of selected hydronium and ammonium/hydronium ..beta..''-aluminas. The ammonium/hydronium and hydronium ..beta..''-aluminas have room temperature conductivities of about 10/sup -4/ and 10/sup -6/ (Omega-cm)/sup -1/, respectively. They do not appear to be distinct and independent materials, but only general compositions in a continuum of protonic ..beta..''-aluminas which contain various concentrations of water and/or ammonia. The results of thermal analyses, crystal structure studies, and ionic conductivity measurements indicate that it should be possible to convert one protonic ..beta..''-alumina composition to another by careful thermal treatment. The ..beta..''-alumina family of protonic compounds is thus a model system for studying the effects of solvation and hydrogen bonding on the motion of protonic species in an oxide lattice.