Thepalatability of plants as food for herbivores depends on chemical composition.In this study, we tested the relative palatability of selected species ofgreen, brown and red algae to a marine gastropod, Littorina striata, usingthe agar suspension method. When fed to snails (Littorina striata), thegreen algae (Ulva rigida and Enteromorpha ramulosa) were readilyconsumed. A brown alga, Fucus spiralis, was eaten moderately and two redalgae (Gracilaria ferox and Laurencia obtusa) were avoided. Whenwe offered the snails mixtures of the most and least preferred species, feedingby the snails stopped when the unpreferred alga, Gracilaria ferox, waspresent in greater proportion than the preferred one, Enteromorpha ramulosa.Whatever the nature of the specific inhibitory agent, its concentrationseaweed to be a more important cue for feeding than the stimulatory one offeredby the preferred algal species.