In the past year, several tests of the hypothesis that NMDA-dependent hippocampal long-term potentiation (LTP) underlies learning have been reported. Data from mutant mice point to a potential role for NMDA-dependent LTP in hippocampal place cell function and spatial learning, but evidence for a causal relation is not yet available. Other studies have shown that robust spatial learning is possible without NMDA-dependent hippocampal LTP. Although the current evidence for the role of LTP in learning is mixed, LTPremains the most promising neural mechanism for associative learning. Several new experimental approaches are now available for future research.