The prediction of extreme environmental loading is critical to the assessment of the structural integrity of all fixed offshore installations. In the last ten years significant improvements have been made both in our understanding of the applied loads and our ability to model them. In particular, the importance of the following processes has been highlighted: the effects of nonlinearities beyond second-order on wave crest elevations; and both the occurrence and the effects of wave breaking on kinematics high in the water column. These effects must be included in a long-term assessment of loading. The calculation of which requires the following:...