Tropical instability waves have been shown to have a major impact on the variability of temperature and nutrients along the equatorial wave guide. In order to assess the impact of these features on carbon species distributions during an ENSO event, sea surface temperature, salinity, sigma-t, nitrate, CO2 fugacity, total inorganic carbon, total alkalinity, and pH along the equator were measured from 130¿W to 100¿W during 8--15 May 1992. Concurrent moored measurements of surface currents and temperature were also made at 0¿, 110¿W. Results indicate that tropical instability waves, with periods of 15 to 20 days and zonal wavelengths of 700--800 km, controlled the observed spatial variability of the CO2 species, nitrate and hydrographic parameters at the equator.