Perhaps the most basic finding in memory research is the repetition effect--the fact that repetition enhances memory. Peterson and Mulligan (2012) recently documented a surprising "negative repetition effect," in which participants who studied a list of cue-target pairs twice recalled "fewer" targets than a group who studied the pairs only once. Words within a pair rhymed and across pairs, the target words were drawn from a small set of categories. In the repetition condition, the pairs were initially presented in a random order and then presented a second time blocked by the category of the target words. In the single presentation condition, the pairs were presented only in the blocked order. Participants in the former condition recalled fewer target words on a free recall test despite having seen the word pairs twice (the negative repetition effect). The encoding conditions necessary to produce this effect were examined in 4 experiments. Presenting the repetitions in a single study list elicited the negative repetition effect in free and category-cued recall. However, eliminating the strong within-trial, rhyme relationship eliminated the effect in both tests. Finally, presenting a disorganized but unrelated set of rhyming word pairs as List 1 reduced recall (relative to the single-presentation condition) to the same degree as the repetition condition. The negative repetition effect is due to reduced interitem relational processing during the presentation of the organized list (or half list), a reduction that requires a competing within-target relationship but can be induced by an unrelated as well as identical set of word pairs.