Pile foundations are subjected to vibratlons due to earthquakes and under machines. The nature and magnitude of vibrations is different under butldings, machines and off-shore structures. The piles may lose contact with soil particularly under lateral vibratlous In this paper, methods of analysis for earthquake (passive) loading and machine (active) loading have been described. A comparison of predicted and measured response shows that there are considerable gaps in present day understanding of the dynamic behavior of single piles as well as piles in groups.