False memories (e.g., recognition of events that did not occur) are considered behaviorally and subjectively indistinguishable from true memories. We report that brain activity differs when true and false memories are retrieved. Strongly associated lists of words were presented to one or the other cerebral hemisphere at study. This led to lateralized brain activity for these words during a centrally presented recognition test, reflecting their lateralized encoding. This activity was absent for nonstudied but strongly associated words falsely recognized as studied items. These results indicate that studied words leave sensory signatures of study experiences that are absent for false memories. In addition, hemifield effects emerged, including a slower reaction time (RT) for false recognition of nonstudied words whose associated lists were presented to the left hemifield (i.e., right hemisphere). These false recognition responses were accompanied by frontal slow wave activity, which may reflect a differential ability of the two hemispheres with respect to semantic processing.