To identify the source of cloud condensation nuclei(CCN) in the marine atmosphere, simultaneous measurements of aerosol chemical components and CCN concentration were made over more than a year at Hahajima, the Ogasawara Islands, located on the Northwest Pacific Ocean in the lee of Eastern Asian large pollution sources. Large loading of CCN in continental air mass and long-distance transportation to the remote ocean were confirmed. Non-seasalt sulfate and water soluble organic carbon were dominant in fine aerosols and their concentration revealed significant relationships with CCN concentration, suggesting that not only sulfate but also organic aerosols play a key role in CCN formation, especially in the background atmospheric condition.¿ 1997 American Geophysical Union