The dielectric behavior of SrTiO3 thin films prepared by the pulsed-laser deposition technique on SrTiO3 single-crystal substrates is studied under dc electric field. A high dielectric constant maximum εmax(∼2280) and a low-loss tan δ (∼0.001) are obtained. Compared with the observation in SrTiO3 single crystals, an additional dielectric loss peak with frequency dispersion is observed around 150 K (at 1 kHz). With increasing dc bias, the peak is suppressed and finally disappears at ∼350 kV/cm; however, the temperature at which the peak occurs is independent of electric field. The possible physical mechanism of the peak is briefly discussed. © 2001 American Institute of Physics.