Some forms of memory, such as novel-object recognition (NOR), can be acquired and retrieved without involving the hippocampus. Rats were exposed to a novel object (the encoding period) followed by a 2-hour period of either wakefulness or sleep. Three weeks after encoding, NOR memory in rats was retained in the sleep condition but not in the wake condition. The effect of sleep on NOR retrieval was abolished by hippocampal inactivation by muscimol delivered during post-encoding sleep but not before encoding or before retrieval. These findings suggest that sleep-mediated consolidation of NOR memory involves the hippocampus.