Semantic priming is traditionally viewed as an effect that rapidly decays. A new view of long-term word priming in attractor neural networks is proposed. The model predicts long-term semantic priming under certain conditions. That is, the task must engage semantic-level processing to a sufficient degree. The predictions were confirmed in computer simulations and in 3 experiments. Experiment 1 showed that when target words are each preceded by multiple semantically related primes, there is long-lag priming on a semanticdecision task but not on a lexical-decision task. Experiment 2 replicated the long-term semantic priming effect for semantic decisions with only one prime per target. Experiment 3 demonstrated semantic priming with much longer word lists at lags of 0, 4, and 8 items. These are the first experiments to demonstrate a semantic priming effect spanning many intervening items and lasting much longer than a few seconds.Many forms of priming have been studied (for reviews, see Monsell, 1985;Richardson-Klavehn & Bjork, 1988;Schacter, 1987). Whereas in repetition priming the priming stimulus is identical to the target, in similarity-based priming tests (e.g., form priming, morphological priming, and semantic priming), the prime and target are different words sharing some surface features, semantic features, or both. Repetition priming and form priming have been found to produce long-lasting effects ranging from hours to weeks or even months (e.g., Bentin & Feldman, 1990; Bentin & Moscovitch, 1988;Jacoby & Dallas, 1981;Rueckl, 1990;Sloman, Hayman, Ohta, Law, & Tulving, 1988). Semantic priming, however, is traditionally thought to produce only short-term effects that dissipate after several seconds or after more than one item intervenes between prime and target stimuli. Is it possible that completely different priming mechanisms are operating at semantic levels of processing as compared with other levels at which priming could occur? The most parsimonious account would be that the same mechanisms operate at all levels of the system. In this article, we are concerned particularly with long-term priming and argue in favor of a single mechanism to account for all types of long-term priming. Our view is that short-term semantic priming involves a process completely different from that underlying long-term priming, but either type of process should behave according to the same computational principles at any level of the system, whether it be perceptual or semantic. Although our account of long-term priming is very general, our focus is specifically on semantic priming because our model makes novel predictions in this domain. We first present a theoretical account of long-term priming based on a distributed cormectionist model of word recognition, combined with some very general learning-processing assumptions. The theory specifies conditions under which long-term priming should occur and predicts that semantic priming should produce long-term effects under the appropriate conditions (even though it has not been fo...