The dielectric parameters and relaxation properties of azo dye (DR1) doped E7 and pure E7 liquid crystal (LC) have been investigated in a wide frequency range of 10k-10MHz through the dielectric spectroscopy method at room temperature. Dielectric anisotropy (Delta epsilon) property of the LC changes from the positive type to negative type and dielectric anisotropy values decrease with doping of DR1. The relaxation frequency f(r) of E7 and E7/DR1 LC was calculated by means of Cole-Cole plots. Influence of bias voltage on the dielectric parameters has also been investigated. (c) 2006 Elsevier B.V. All rights reserved.