Haliotis discus, a useful abalone of herbivorous gastropod, shows feeding preference tomarine algae depending upon their growth stage and recognition of taste. This study was carriedout to investigate this abalone’s algal preferences and the presence of feeding stimulants. Insingle-choice experiments the small(S) group generally preferred Ulva pertusa(Chlorophyta),whereas the medium(M) and large(L) group preferred both Laminaria japonica(Phaeophyta)and Undaria pinnatifida(Phaeophyta). In multi-choice experiments using 4 algal species of L.japonica, U. pertusa, U. pinnatifidaand Ecklonia cava(Phaeophyta), the results were same as inthe single-choice experiments; the S group preferred U. pertusathe most, while the M and Lgroup preferred both U. pinnatifidaand L. japonica. However E. cavawas not preferred by anygroups. In order to examine the presence of feeding stimulant, chemical compounds from algae usedas feed were isolated and identified. The abalone responded to water soluble matters of L. japo-nica, U. pinnatifidaand U. pertusa, but those of E. cavaand Sargassum sagamianum(Phaeophyta)were not attractive to them. In feeding stimulant experiments using fat soluble matters, the S grouppreferred the fat soluble matter of U. pertusathe most, while the M group and the L group pre-ferred those of U. pertusaand U. pinnatifida, and those of L. japonica, respectively. However the fatsoluble matter of S. sagamianumwas not attractive to the abalone. The results of feeding sti-mulant experiments were same as those of single-choice or multi-choice experiments, which show-ed that compound lipids in fat soluble matter might act as feeding-stimulant.