The starfish Coscinasterias calamaria feeds predominantly on mussels (Mytilus edulis) on subtidal rocky reefs in Port Phillip Bay (Victoria, Australia), but also eats many other benthic invertebrates, especially molluscs. The blacklip abalone Haliotis rubra was rarely eaten on most reefs, but aggregations of the starfish were found feeding on abalone at some times and places where other suitable prey were scarce. Where abalone were eaten, a higher proportion of small abalone were eaten than larger ones. Starfish preferred small abalone to mussels of the same weight in laboratory choice experiments, and the time required for the starfish to eat mussels and abalone of the same size were similar. Previously unobserved aspects of the escape response of abalone may explain the variable rate of predation on abalone by C. calamaria. Abalone displayed various behavioural responses to attack that increase the likelihood of escaping. One response apparently involves the production of a chemical deterrent in the abalone epithelium. It appears that as a result abalone are not often eaten unless mussels stocks are depleted and the starfish are at high densities. This is most likely on offshore reefs where abundant mussel recruitment in most years sustains large numbers of C. calamaria.