[en] The ionic hopping conductivity is shown to have the frequency dependence sigma(ω) = sigma(infinity) - [sigma(infinity)] - sigma(0)]/(1 + ω²tau²) in two simple models: (i) a general two-inequivalent sublattice system with no interactions other than exclusion of double-site occupancy; (ii) a linear chain of equivalent sites with nearest neighbor interactions as well as double-site-occupancy exclusion. The characteristic time tau for frequency dependence can be much shorter than a hopping time tau/sub dc/ inferred from dc conductivity; and sigma(0)/sigma(infinity) increases to unity at high temperatures. These features agree qualitatively with data on Na β-alumina