This thesis report documents the analysis of several aspects of wave action on offshore monopile foundations. The first part deals with the run-up phenomenon on monopiles and strives to arrive at a modified run-up factor using previously conducted laboratory tests. The second part focuses on slamming forces and pressures on platforms on monopiles. Both solid and grated platforms with different solidity are analysed. Results from run-up and laboratory results for forces and pressures are used to obtain slamming coefficient and grate multiplication factor for platforms. In the final part of the report, results for wave forces from the recent experiments conducted in AAU for monopile foundation models are analysed. The objective is to study the effect of secondary structures on monopiles by attaching a simple cylindrical element to the model. The experimental results are also compared with the existing theories. Finally the conclusions from the entire study are presented.