The paper deals with the influence of past loading history on the seismic response of earth dams by interpreting the static and dynamic behaviour of a real case-history: the El Infiernillo Dam. Settlements, pore water pressures and accelerations measured during different stages of the dam lifetime have been interpreted by using a coupled dynamic approach derived from the u–p formulation of the Biot consolidation theory. The approach is solved numerically with the finite element method. The study firstly investigates the effectiveness of the adopted model to predict the observed dam behaviour. Following, a parametric study has been performed to examine what effects, additional loading histories, have on the prediction of seismic-induced freeboard loss. The study brings out soil hardening effects induced by the past seismic history, and investigates to what extent earth dam response to a given earthquake may be affected by previous seismic events.