There is a long way between the simple design wave of the seven ties and the metocean design conditions requirements for offshore engineering in the twenty-first century. On the basis of the conclusions of workgroups of the Offshore Oil and Gas and Shipping industries, we review the needs that appeared with new types of structures and new ways of utilizing them and the state of the Art of the response of the research community to these Demands. Especially, emphasis is made on wave conditions in the very high and very low frequency parts of the spectrum and on other phenomena exciting natural modes around a few minutes periods, on extreme wave and crest heights that may seem to question current design practice, on the increasing importance of ensuring un- interrupted exploitation in addition to resisting to the most extreme sea conditions, on non-stationary gust- like phenomena such as current rapid changes and squall winds at low latitudes, on the problems associated with the definition of design current profiles, or on the reliability of hindcast and other data sources, especially for joint occurrence of various loading factors.
In the seventies, doubts about what should be the right, height for the hundred year wave in the North Sea have triggered a large amount of scientific efforts and joint industry performance monitoring campaigns for characterizing the metocean environment. After some return on experience, it appeared in the eighties that most structures were neither undersized nor overcostly conservative. It en followed a reduction in efforts, since many managers believed that designers knew all that would ever be needed to know about waves and probably wind and currents also since the design was at that time, governed by the highest wave that would ever be encountered.
