Lower bound dynamic shakedown theory is a limit state method. It is employed herein to investigate the safety, which is associated with permanent displacement, of slopes under repeated dynamic loads, mainly earthquakes. An efficient numerical method, previously applied to the static shakedown of pavements, is extended to the dynamic shakedown of slopes in this study. It is shown that dynamic shakedown, unlike other limit state methods, is able to consider the dynamic properties of both the load and subsoil. The effect of the soil strength parameters and dynamic features of the soil and loads are examined thoroughly and some illustrative examples are employed. The short-term and long-term behavior of slopes under seismic loads are studied as well, comparing results of the present study with the well-known displacement method of Newmark.