In certain regions of the world, designing deep foundations to withstand seismic loading is a reality. Seismic loading of structures and foundations reaches its most critical state as a cyclic lateral force. The response of soils and foundations to repetitive lateral forces is highly complex, relegating most design methods to be based upon overly conservative rules-of thumb. The primary objective of this research was to analyze the mechanics of seismic loading on pile groups in clay soils. To achieve this a model testing facility was constructed to house a fully instrumented 1 3 5 model pile group that was subjected to cyclic lateral loading. An empirically based method for pile group design is suggested based upon the results generated from model pile group testing.