Data from 20 satellite-tracked drifting buoys deployed in the eastern equatorial Pacific Ocean during the summer of 1979 were used to investigate the nature, effects, and energetics of currents associated with cusp-shaped long waves observed in satellite IR imagery of the sea surface during all except El Ni¿o years. It is shown that the long waves are associated with a vigorous pattern of mesoscale eddies lying primarily between the equator and 7¿N. The spatial structure of the eddy kinetic energy closely resembles the eigenfunctions obtained from Philander's (1978) investigation of barotropic instability of that part of the South Equatorial Current lying north of the equator. Computation of the energy exchange between the eddies and the mean field suggests an e folding time of about two weeks for the eddies and a braking effect on the mean flow comparable to a change of surface wind stress of a few tenths of a dyne per square centimeter. The eddies also effect an equatoward transport of heat that amounts to about two thirds of the poleward heat transport of the divergent Ekman transport in the near-surface waters.