Fast-ion conduction in solids is considered a paradigm for structure-property relation where ionic conductivity σ = nqµ, n the concentration of charge carrier q, and µ. the mobility of the carrier. The critical conductivity determining factor, ceteris paribus, is the carrier mobility which depends on the geometry of anion array and structure in the solid. Factors inherent in the structural framework include “free” volume, “bottleneck” size, lattice disorder, etc. Other non-structural factors that can play a vital role, even a dominant role, in enhancing ionic conductivity are charge carrier concentration, ion-ion interactions or bonding characteristics, vibrational amplitudes of neighboring ions, lattice compressibility or resiliency, rotational motion of anions, ion size, etc. Many aspects of these factors will be examined in the light of recent studies and the results on some isostructural and isomorphous sulfates and other related structures to evaluate their relative contributions.