This report briefly reviews the ocean surface characteristics that affect radar echo and summarizes the present status of knowledge of the sea echo as a function of radar grazing angle, sea state and wind, polarization, frequency and other factors. The attempts made in the past to provide theoretical models describing the sea echo are reviewed and lead up to the presently accepted models of scattering surfaces composed of the larger gravity waves on which are superimposed the smaller capillary waves. The influence of sea echo on radar design is discussed and is considerably different than the usual design restraints imposed by thermal noise. The potential application of radar for oceanographic measurements such as sea state and wind is described.