Organic carbon concentration and isotopic composition were determined in samples of atmospheric particulate matter collected in 1979 at remote marine locations (Enewetak atoll, Sargasso Sea) during the SEAREX (Sea-Air Exchange) program field experiments. Atmospheric Particulate Organic Carbon (POC) concentrations were found to be in the range of 0.3 to 1.2 &mgr;g. m-3, in agreement with previous literature data. The major mass of POC was found on the smallest particles (r<0.5 &mgr;m). The 13C/12C of the small particles is close to the one expected (Δ13C = 26¿20/∞) for atmospheric POC of continental origin. For all the samples analysed so far, it appears that more than 80% of atmospheric POC over remote marine areas is of continental origin. This can be explained either by long-range transport of small sized continental organic aserosols or by the production of POC in the marine atmosphere from a vapor phase organic carbon pool of continental origin. The POC in the large size fraction of marine asrosols (<20% of the total concentration) is likely to have a direct marine origin since its carbon isotopic composition is close to the expected value (Δ13C = -21¿20/00) for POC associated with sea-salt droplets transported to the marine atmosphere.