Although the load applied on a pile is usually a combination of a vertical and a lateral load, there have been few studies done on the response of piles subjected to combined loading. In addition, the results available in the literature are inconsistent with respect to the effects of axial loads on the lateral response of piles. This book presents the results of model pile load tests performed on model driven and nondisplacement piles to assess the influence of axial loads on the lateral response. The results of the load tests in sand under axial, lateral, and combined loading were compared with results from full-scale tests reported in the literature and predictions from theoretical solutions. The combined load test results showed that the presence of an axial load on piles detrimental to its lateral capacity, for the lateral deflection of the model pile head increased with increasing axial load. The bending moments at the pile head increased substantially in the presence of axial loads. Those results imply that it is unconservative to design piles assuming that there is no interaction between axial and lateral loads.