The diffuse dielectric anomaly is a well-known dielectric relaxation behavior of perovskite oxide materials, which is commonly observed in the temperature range of 400-700 degreesC. However, the detailed mechanism of the relaxation phenomenon is not clearly understood yet. The suggested relaxation models do not explain why the dielectric relaxation behavior appears as the temperature-dependent diffuse: peak. It is believed that previous studies have mainly focused on the frequency dependence of the dielectric relaxation and the variation of the relaxation time, which are usually characterized with the thermally activated process. In this study, we systematically investigated the temperature-dependent behavior of the dielectric relaxation with the remodified Debye equation in the ceramic and the single crystals of BaTiO3. We have confirmed that the diffuse dielectric anomaly is due to the competitive effects between the dielectric relaxation and the disturbance of the electrical conduction. We also suggest that the variation of the relaxation strength is related with the electrical conductivity. 2002 Published by Elsevier Science Ltd.