Recently evaluated flux formulas were used with an edited ship-of-opportunity data set for the 1970's decade to derive estimates of the individual surface heat fluxes and the total or net surface energy exchange for the eastern tropical Pacific. Absorbed solar radiation is the dominant heat flux in the region, and latent heat exchange is the second most important component; total cloud cover and wind speed are generally the most significant atmospheric variables. Over much of the area, the annual excess of net surface flux appears to be balanced by heat advection in the South Equatorial Current. Although the seasonal cycles of sea surface temperatures seem to be produced by variations in net surface flux over parts of the area, they do not appear to balance off Peru and near the equator. Instead, water temperature seems to be noticeably affected by the seasonal cycle of upwelling and advection along the Peru coast. This data set was also used to derive sea surface temperature and net surface heat flux departures from the mean for individual months during the 1972 El Ni¿o. The magnitude and speed of the initial warming along the eastern ocean margin indicate changes in heat content at least an order of magnitude greater than any departures of net surface flux; this fact and the subsequent poleward and westward spreading of warm water support an advective origin, especially Wyrtki's hypothesis of an eastward propagating Kelvin wave. Subsequent changes during an El Ni¿o episode also do not seem to be influenced appreciably by variations in surface heat exchange.