Pile foundations are widely used both onshore and offshore to transfer heavy structural loads to competent load-bearing soil strata or bed rock. Geotechnical engineers are called upon to design deep foundations when the shallow layers of soils beneath the building are either unable to support the loads imposed by the superstructure on the shallow foundations or if the shallow layers may become unstable due to the cyclic shear stresses induced by the earthquake loading. Under such circumstances, it is imperative to look for pile foundations that transfer the load from the superstructure to more firm and stable soil strata at deeper levels or onto bed rock. In this chapter, the seismic design of pile foundations is considered in the light of the EC8 provisions as well as some of the current research findings. It is perhaps helpful if some of the well-known examples of failures of pile foundations during or following an earthquake loading are considered first.