Survival of the tubicolous amphipod Ampelisca abdita in a sediment toxicity test was negatively correlated with the presence of indigenous Nephtys incisa. The gut contents of N. incisa held in uncontaminated sediment included identifiable portions of the amphipods A. abdita and Microdeutopus gryllotalpa. Although most nephtyid polychaete worms are active predators, Nephtys incisa has been considered a nonselective deposit-feeder. It is concluded that N. incisa will prey upon amphipods under laboratory conditions. This predation may be a factor in the exclusion of surface-dwelling amphipods from the Nephtys-Nucula community common in southern New England. (Copyright (c) 1989 Estuaries Research Federation.)