The papers which follow were presented at an International Sym­ posium held in Lisbon from 8-11 July 1985 on the Hydrodynamics of Ocean Wave-Energy Utilization and sponsored by the Interna­ tional Union of Theoretical and Applied Mechanics. The subject of the Symposium embraced wave statistics, numerical methods, theoretical, experimental and field studies of wave­ energy devices. The idea of extracting useful energy from ocean waves continues to attract the curiosity of scientists and engineers in many parts of the world as the following papers indicate. Increasing­ ly the trend is towards smaller devices suitable for use near remote island communities where wave power, as an alternative to costly diesel fuel for electric generators, is already very competitive in economic terms. The decision to build two different prototype wave-power devices into the cliffs off Bergen in Norway has provided a welcome impetus to the field, stimulating a large amount of theoretical work on oscillating water column-type devices. In particular phase control methods - in which force and velocity of a rigid body, or pressure and volume flux across a turbine are matched in phase to achieve maximum power output - rightfully occupy a central place in the papers that follow. In addition to the established workers in the field, a new ge­ neration of wave-energy enthusiasts is emerging, learning from the mistakes of others and contributing exciting ideas of both a conceptual and practical nature.