Fourteen species of Opisthobranch molluscs are cited from the Gymnesian Is. (Majorca and Minorca); at least eleven of them are new citations for these poor-searched islands, and six for the Balearic archipelago. Most species are banal and well-known on the nearby mainland coasts, but Elysia timida, Phyllaplysia lafonti and Phyllidia pulitzeri constitute uncommon records