The feeding biology of nemerteans is reviewed, new information is presented, and the role of nemerteans in natural communities is discussed and evaluated. Most nemerteans are carnivorous, the majority feeding on live, often specific, prey, while some are scavengers. Macrophagous feeding is found in the Palaeonemertea, Heteronemertea and some of the Hoplonemertea; the more specialized suctorial feeding is limited to five of the hoplonemertean families, and suspension feeding (omnivorous diet) occurs only in the highly specialized symbiotic monogeneric Bdellonemertea. Feeding adaptations seem to be related to the nature and employment of the proboscis, the dilatability of the mouth, and the structure of the anterior part of the digestive tract. The transport of dissolved organic materials from seawater has been demonstrated, but its role in nemertean nutrition is just being contemplated. Present meager information on predation has shown nemerteans to have actually and potentially large effects on prey populations and thus on the communities in which they live. As the feeding biology of only a relative handful of species has been studied, much basic comparative research is needed before we can corroborate or refute our present ideas concerning the ecological roles of nemerteans.