We have derived a simple, analytic formula for the prediction of the effective dielectric constant of binary 0-3 composite materials. In comparison with a popular formula in the field ( Jayasundere and Smith [ 1]), it gives the expected asymptotic value for the internal electric field of the inclusions when their total volume fraction tends to one. It is also applicable to the whole range of the volume fraction of the inclusions and is reasonably good for all values of the dielectric constants of the constituents. For non-conductive constituents, it gives effective complex permittivity prediction that fits well to experimental data, out-performs the Jayasundere- Smith formula and a linearized version [ 2, 3] of the well-known Bruggeman formula. (C) 2004 Kluwer Academic Publishers.