In this work, ceramic CaCu3Ti4O12 has been prepared by a conventional solid-state route. The samples present rectifying properties. The study of the I-V curve with the sintering time shows an evolution of the nonlinear coefficient and the increase of barriers suitable to rectify. The dielectric constant increases with the sintering time, following the same trend observed for the number of rectifying barriers. This suggests the existence of a close relation between the barriers that produce electric rectification and the insulating barriers producing the high dielectric constant by the insulating barrier layer capacitor effect.