Temperature, salinity, velocity, and wind from a mooring at 0¿N, 23¿W are used along with satellite data for sea surface temperature and sea level to examine the contribution of tropical instability waves (TIWs) to the energy and heat balance of the equatorial Atlantic mixed layer. The TIWs appear as periodic 20--30 day fluctuations of currents, temperature, and salinity, which intensify beginning in June and peak in late boreal summer. The intensification occurs in phase with strengthening of the southeasterly trade winds and the seasonal appearance of the equatorial tongue of cold mixed layer temperatures. In 2002 these waves, which warm the mixed layer by 0.35¿C during summer months, are maintained by both barotropic and baroclinic conversions that are of comparable size. Salinity fluctuations, previously neglected, increase the magnitude of baroclinic energy conversion.