The appearence of organochlorine pesticide residues in some marinealgae, e.g. Sargassum thunbergii, Ulva pertusa, Codium fragile, and Enteromorpha linza, collected from various sites of Kwang Yang Bay, southern coast of Korea, was surveyed through the year from May 1974 to March 1975. The residues were found to appear in the order to July>September>May>November≒March≒January; $alpha$-BHC>heptachlor epoxide>dieldrin>aldrin>endrin; and in the range of 0-93 $mu extrm{g}$/kg dry matter.