In Experiment I, ten garter snakes (Thamnophis sirtalis sirtalis) accustomed to a diet of fish were injected with either lithium chloride or normal saline thirty minutes after their ingestion of worms (models). On extinction days, the subjects were offered both fish that had been dipped into an extract prepared from the surface substances of worms (mimics) and untreated fish. The lithium chloride injected subjects responded with significantly longer latencies to the mimics than did the saline injected subjects, while both groups responded with similar short latencies to the untreated fish. In Experiment II, six garter snakes were injected with either lithium chloride or saline following their ingestion of the model worms. On extinction days, the subjects were offered fish that had been dipped into guppy or cave salamander extract in addition to the mimics and untreated fish. The lithium chloride injected subjects responded with longer latencies to the mimics than did the saline injected subjects. Both lithium chloride and saline injected subjects responded with similar latencies to the other prey offered. The above experiments demonstrated the theoretical viability of the concept of olfactory mimicry. It appears that garter snakes will reject normally edible minnows that bear an olfactory resemblance to worms after they have experienced a delayed toxicosis subsequent to their ingestion of the worms (Experiment I). Furthermore, this aversion is specific to the mimics and not the result of a toxicosis-induced neophobia which would lead to the serpents' rejection of all novel prey (Experiment II) .