The gastropod Calliostoma canaliculatum displays a series of aggressive escape behaviors upon contact with tube feet of the predatory seastars Pycnopodia helianthoides and Pisaster giganteus. Escape behaviors are predator specific. Calliostoma canaliculatum moves away from contact with P. giganteus more frequently than P. helianthoides, clamping down with the foot or retracting the head and foot into the shell when exposed to P. helianthoides. If escape from the grasp of either seastar fails, C. canaliculatum releases a yellow-colored exudate from the hypobranchial gland and subsequently retracts both the head and foot fully into the shell. This exudate contains noxious compound(s) as evidenced by retraction of tube feet and arms away from the exudate in both seastars. Tube foot retraction responses to dilutions of the exudate indicates that both species of seastars are able to detect the exudate at a concentration of 3.2 X 10-3 mg exudate/ml seawater. Pisaster giganteus is more responsive to the exudate than Pycnopodia helianthoides, moving away from the source as well as retracting the tube feet and arm. Snails spread the exudate over their shells with their foot, perhaps to ensure defense from predators for some time period after exudate release. The exudate was collected and extracted in chloroform-ethyl acetate (1 : 1), then fractionated using flash chromatography. The most bioactive fraction, as evidenced by tube-foot retraction, was soluble in ethyl acetate and appeared to contain two major compounds.