The repetition and the predictability of a word in a conversation are two factors that are believed to affect whether it is emphasized: predictable, repeated words are less acoustically prominent than unpredictable, new words. However, because predictability and repetition are correlated, it is unclear whether speakers lengthen unpredictable words to facilitate comprehension or whether this lengthening is the result of difficulties in accessing a new (nonrepeated) lexical item. In this study, we investigated the relationship between acoustic prominence, repetition, and predictability in a description task. In Experiment 1, we found that repeated referents are produced with reduced prominence, even when these referents are unexpected. In Experiment 2, we found that predictability and repetition both have independent effects on duration and intensity. However, word duration was primarily determined by repetition, and intensity was primarily determined by predictability. The results are most consistent with an account in which multiple cognitive factors influence the acoustic prominence of a word.