The (1 - x)BaTiO3-x(Bi3/4Na1/4)(Mg1/4Ti3/4)O-3 (0.2 a parts per thousand currency sign x a parts per thousand currency sign 0.9) ceramics were prepared by conventional solid-state reaction route. Their dielectric properties were found to follow a modified Curie-Weiss law and an empirical Lorenz-type relation in respective temperature regions. Their dielectric relaxation times fit well with the Vogel-Fulcher relation for x = 0.2, 0.3, and 0.4. For x = 0.5, 0.6, 0.7, and 0.8, however, the fitting curves of Vogel-Fulcher relation showed certain deviation from the experimental data. Based on the theoretical treatment of Landau-Ginsburg-Devonshire theory, an approximate treatment of the E-field dependence of the permittivity was adopted and found to describe well the field dependence of the permittivity for x = 0.3 at temperatures equal to and below T (m) (temperature of maximum dielectric permittivity). A combined Langevin-type expression used in the present work appears to give a good account for the field dependence of the permittivity, assuming polar regions are of a statistical cluster size. For polar clusters of linear dimension L similar to 4-8 nm for instance, the fitted values of polarization are in the range of P similar to 6.2-9.8 mu C/cm(2).