Experimental results of nonlinear wave loads acting on submerged cylinders by using fairly large models are presented. Nonlinear effects of the incident wave amplitude, the cylinder submergence and the cross-sectional geometries are studied. Those results are compared with the numerical calculations to the second-order. The calculation method is based on the regular perturbation theory and the wave loads are obtained by the integration of hydrodynamic pressure over the body surface. The fluid is assumed inviscid, incompressible, homogeneous and infinitely deep. Consequently, when the cylinder is placed appropriately deep, the second-order theory agrees well with the experiments. However, when the cylinder is close to the free surface, the theory would overestimate the wave loads obtained by the experiments. In this case, the nonlinear such as wave breaking would be significant.