The ionic conductivity of (1 − x)Ag 2 SO 4 (x)M 2 SO 4 (where x = 0 to 0.07 and M = Li, Na, K, Rb and Cs) has been systematically investigated by using complex impedance spectroscopy. The solid solubility limits up to 3 mol% of M 2 SO 4 in β-Ag 2 SO 4 has been set with X-ray powder diffraction and scanning electron microscopy techniques. The transport number obtained at different temperatures using Wagners d.c. polarization method shows negligible electronic contribution. The conductivity behaviour appears to be strongly dependent on the magnitude of difference in ionic radii of host and guest. The lattice structure related term has been correlated to ionic conductivity to explain the results.