From the dinoflagellate Coolia monotis, a new ceramide (1) bearing a 2-hydroxy-15-methyl-3-octadecenoyl moiety was isolated as a cellular constituent. The structure, including the partial absolute configuration, was elucidated as 1 on the basis of the 2D NMR of 1, and chiral HPLC and CD examinations with benzoyl derivatives of its degradation products. To our knowledge, this is the first example, from