We study electrostatic parallel-plate actuators operated in dielectric liquids. The stable operation zone of the actuators in common liquids is extended far beyond one-third of the initial gap, which is the typical limit of stability for such actuators operated in air. The pull-in effect can even be totally suppressed. In spite of higher dielectric constants in liquids than in air, which is expected to magnify the electrostatic forces, the required voltages to actuate are not significantly reduced and may even be larger. These results are discussed with regard to the dielectric constant of the liquids and to the electrical insulating layers of the parallel plates which appear to play a major role. Finally, the analytical approach is compared to experiments performed on fabricated devices.