The design of piles under seismic loads is conventionally carried out with reference to the inertial forces arising from structural vibrations and, hence, neglecting kinematic interaction between pile and soil. Even if in the last years several research efforts gave particular attention to kinematic effects, they focused on bending moments at the interface between two soil layers with different stiffness, while few contributions investigated kinematic effects at pile head. The paper presents the results (both in the frequency and time domain) of extensive parametric studies, leading to a simplified formula for predicting kinematic bending moments at pile head. The paper gives some indications about their relative importance with respect to the inertial ones and provides simply rules to combine inertial and kinematic maximum effects taking into account their phase lag.