We present the results of a series of research flights over the eastern equatorial Pacific that took place during various stages of the 1982--1983 El Ni¿o/Southern Oscillation (ENSO) event. A continuous background was provided by satellite observations of significant convection (highly reflective cloud) and of atmospheric moisture and stability obtained from the TIROS Operational Vertical Sounder (TOVS). TOVS data showed a progressive moistening and destabilization of the lower troposphere in the eastern equatorial Pacific. Between April and July 1983, frequent periods of organized convective activity in this area were associated with incursions of surface westerly winds originating in the central and western Pacific. The flights across the equator in the eastern Pacific in early January 1983 recorded large positive sea surface temperature anomalies and corresponding strong moisture flux from the ocean to the lower troposphere, although there were no episodes of significant convection in the area until February 1983. A comparison with non-ENSO conditions is provided by the data from a flight along a similar track in 1980. Flights in July and September 1983 took place after the reestablishment of trade winds in the area and show a gradual return toward normal conditions in the meteorological variables examined.