The response of piles due to lateral movement of liquefied soils is discussed in this paper. To investigate the effects of ground improvement, liquefaction and lateral spreading of liquefied soils, detailed analyses of a well-documented case history of an oil tank on pile foundations were carried out. Two series of analyses were conducted so as to separate and comparatively examine the pile responses during the cyclic liquefaction and subsequent lateral spreading of the ground. It was found that liquefaction of the fill deposits developed after only two cycles of strong shaking, and that at this early stage of shaking, the maximum ground and pile responses due to cyclic loads were induced. Thus, part of the damage to the piles was caused in the course of the cyclic ground deformation and solely due to effects of cyclic liquefaction. Further and larger damage to the piles was caused during the subsequent lateral spreading of the liquefied soils. In both loading phases, i.e. dynamic phase and lateral spreading phase respectively, the large lateral ground displacement was the key factor influencing the pile response. Results of the numerical analyses reveal that a ground improvement by sand compaction piles reduced the deformation in the foundation soils and improved the performance of the piles.