The tropospheric trace constituent formaldehyde, HCHO, was measured in rain and in the gas phase during the wet season at Enewetak Atoll, a remote marine site in the central equatorial Pacific. Rainwater averaged 8¿2 &mgr;g/kg; the gas phase averaged 0.4¿0.2 ppbv (0.5 &mgr;g/m3). These values, especially the rain, are among the lowest reported to date. The formaldehyde flux to the sea by rainout and washout extrapolates to 0.010 g m-2 y-1. The gaseous flux into the sea surface is estimated to be 0.05 g m-2 y-1 by an air-sea exchange calculation that takes into account enhanced uptake by hydroxide-catalyzed formaldehyde hydration. The measured mixing ratio is close to the 0.18 ppbv prediction of a tropospheric chemistry model calculation. The methane oxidation chain probably is the sole formaldehyde source in the Enewetak area. The total formaldehyde flux as carbon into the ocean is ~2% of the estimated total organic carbon from rainout and washout. About 2--4% of the calculated column formaldehyde production is removed from the atmosphere by these processes.