The prefrontal cortex plays a critical role in recollecting the temporal context of past events. The present study used eventrelated functional magnetic resonance imaging (fMRI) and explored the neural correlates of temporal-order retrieval during a recency judgment paradigm. In this paradigm, after study of a list of words presented sequentially, subjects were presented with two of the studied words simultaneously and were asked which of the two words was studied more recently. Two types of such retrieval trials with varied (high and low) levels of demand for temporal-order retrieval were intermixed and compared using event-related fMRI. The intraparadigm comparison of high versus low demand trials revealed brain regions with activation that was modulated on the basis of demand for temporal-order retrieval. Multiple lateral prefrontal regions including the middle and inferior lateral prefrontal cortex were prominently activated. Activation was also observed in the anterior prefrontal cortex and the medial temporal cortex, regions well documented to be related to memory retrieval in general. The modulation of brain activity in these regions suggests a detailed pathway that is engaged during recency judgment.Key words: recency; prefrontal; memory; retrieval; context; fMRIThe prefrontal cortex has been implicated in several types of mnemonic functions (Stuss and Benson, 1986;Fuster, 1997). Among them is recollection of the temporal context of past events, an ability that has most often been tested using recency judgment paradigms in which two events are to be judged as to which has occurred more recently (Yntema and Trask, 1963). Since the initial report in Milner (1971), several neuropsychological studies of humans and monkeys have provided evidence that damage to the lateral prefrontal cortex impairs temporal-order retrieval and that the effect of damage is greater in retrieving the temporal order of past events than in retrieving the past events themselves (Shimamura et al., 1990;Milner et al., 1991;Petrides, 1991;Butters et al., 1994). Previous neuroimaging studies investigating recency judgment used this temporal-order versus item retrieval contrast and revealed prefrontal activation associated with temporal-order retrieval relative to item retrieval (Eyler Zorrilla et al., 1996;Cabeza et al., 1997Cabeza et al., , 2000.The contrast of the dichotomous temporal-order versus item retrieval is useful in detecting functional characteristics that are differential among particular brain regions, as is most typically used in the demonstration of double dissociation between regions. However, this approach leaves unspecified the brain activity related to temporal-order retrieval itself at a whole-brain level because, for instance, it is possible that brain activity common to temporal-order and item retrieval is subtracted out even when the activity is related to temporal-order retrieval. An alternative approach complements the previous approach and allows us to uncover the whole neural correlates of temporal-order retr...