Holothurins were isolated from two Species of sea cucumbers, Psolus fabricii and Cucumaria frondosa, captured in different locations along the north shore of the St-Lawrence gulf and estuary. This is the first example of the oresence of saponin-like substances in a species of the family Psolidae. Physico-chemical evidence indicates the triterpene glycosidic nature of these bio-active compounds. Structural analyses were conducted on the triterpene and sugar moities resulting from acid solvolyses of the holothurins as well as on the intact glycosides. Partial structures 40 and 43 are proposed for these species.