An analysis of wave data from the NE Atlantic shows that the average power density along the UK west coast is about 80 kW m-1 or 120 GW overall, more than twice the installed capacity of the CEGB. The Jl'.)wer supply is also extremely variable, for 1% of the year in excess of 1 MW m-1 and for a further 1% very close to zero. This variability not only creates severe technical problems in any attempt to harness wave power, but the lack of firmness means that the value of any power brought to shore is limited to the value of other forms of energy which can be so conserved. This value depends on many factors including fuel cost escalations and the load factor of the wave power supply, but initial estimates indicate that it could be of the same order as the cost of installing a wave power system. In addition to describing some of the prom1s1ng devices which could be used for extracting wave power, the problems associated with designing a conversion and transmission system to link the variable supply of energy at the device into a system, meeting the more even requirements of the consumer are discussed. It is shown that it may be possible to tailor the device and conversion plant characteristics to achieve this power regulation without the need for excessive overload ratings and large quantities of storage. The importance of obtaining a proper understanding of the 'seakeeping' characteristics of devices at sea in a wide range of operating conditions and with realistic power take off systems is emphasised and questions of survival, reliability, maintenance and plant life and the environmental impacts of wave power are also considered. Very rough estimates of the cost of wave power systems suggest that a capital cost of £400 to £800 per kW is possible and it is concluded that if satisfactory solutions can be found to the many remaining technical and engineering problems without an undue increase in this cost, there is a possibility that wave power could make a valuable contribution to Britain's energy needs.