We investigate the dielectric properties of c-axis-oriented epitaxial CaCu3Ti4O12 thin film prepared by pulsed laser deposition. The dielectric constants are found to be in the order of 10(3)-10(4), depending on the mean grain size for the as-deposited thin films. Furthermore, ac conductivity is measured in the frequencies of 0.1-100 kHz and temperatures of 77-350 K. We find that the dissipation is due to hopping polarization of charge carried at high frequencies and is influenced by interfacial effect at low frequencies. Our results of high dielectric constant and its variation with temperature, the low dielectric loss and the stability of the film show that CaCu3Ti4O12 thin film may become a good candidate for certain technological applications. (C) 2003 Elsevier B.V. All rights reserved.