Calicogorgins A, B, and C, three novel sphinganine derivatives possessing lethal and repellent activities against the muricid gastropod Drupella fragum, have been isolated from the gorgonian Calicogorgia sp. and their structures determined on the basis of spectroscopic and chemical evidence. It is currently known that aggregates of muricid gastropods of the genus Drupella are capable of significant destruction of scleractinian corals representing a serious threat to coral reefs. On the other hand, it is well known that most of octocorals, which lack calcareous external skeletons to avoid predation, are relatively free from Drupella attack in the same marine habitats suggesting that they are protected from gastropod predation by toxic or noxious chemicals, i. e. defense allomones. During a search of the biologically active constituents of marine invertebrates, we found that the methanol extract of the gorgonian Calicogorgia sp. showed lethal and repellent activities against D. fragum. Bioassay-directed fractionation of the extract led to the isolation of three new 3-ketosphinganine derivatives, named calicogorgins A, B, and C. The present paper concerns with the structures of these new compounds.