The response and stability of rock slopes during earthquakes are of great concern in relation to transportation facilities, major rock engineering structures such as dams, nuclear power plants and buildings. The rock mass always contains some structural weaknesses such as faults, bedding planes, fracture zones and joints. These structural weaknesses may lead rock slopes to fail in different modes. One of the common failure forms is planar sliding if the major discontinuity plane daylight on the slope surface. The rock slopes may also contain ground water, which drastically influence the effective stress conditions within the slope. In some cases, rock slopes may be fully immersed within the reservoir of dams. When rock slopes are subjected to seismic loads, their stability may be in danger and they may result in their failure. The authors have undertaken an experimental study on the planar sliding mode of rock slopes subjected to gravitational and/or dynamic loads under dry and immersed conditions. The material of model slopes is Ryukyu limestone. The model slopes are subjected to seismic loads under both dry and immersed conditions. The movement of the unstable block, accelerations, and sliding displacements are monitored during the experiments. Some dynamic limiting equilibrium and numerical methods are used to simulate the observed responses of the model slopes. The authors present the outcomes of this experimental program on the planar sliding mode of rock slopes and investigate the principal parameters affecting the behavior of stability of rock slopes through the dynamic limiting equilibrium and numerical methods and discuss their implications.