Auditory and auditory+visual massed repetition served to examine semantic satiation in young and older adults and to understand the possible sources of this phenomenon. In Exp. 1, participants either heard or heard and saw prime words (ROYALTY) repeated 2, 15, or 30 times and made relatedness judgments on targets that were either semantically related (queen) or unrelated (box) to the repeated word. To distinguish satiation from general boredom, semantic satiation was operationally defined as a repetition-induced change in the difference between related and unrelated pairs (relatedness effect). Auditory massed repetition, either alone or in conjunction with prolonged visual exposure, produced semantic satiation effects in both young and older adults. In Exp. 2, participants heard the prime words of the earlier experiment, each repeated 30 times and reported perceptual changes (verbal transformations) during the repetition treatment. In this experiment, older adults were less susceptible to this type of habituation. The discussion focuses on the mechanisms that may be responsible for producing semantic satiation effects in young and older adults with different forms of massed repetition.