Studies with invertebrates and vertebrates have strongly implicated the CREB/CRE transcriptional pathway in long-term memory (LTM) and transcriptionally-dependent L-LTP. It is hypothesized that LTM and L-LTP are both dependent upon a Ca2+ signal generated through activation of NMDA receptors. This review discusses evidence that Ca2+ signals generated through activation of NMDA receptors coactivate the Erk/MAP kinase and cAMP signal transduction pathways. It is hypothesized that activation of these two regulatory pathways increases the transcription of a family of genes through the CREB/CRE transcriptional pathway. Gene disruption studies have shown that Ca2+ activated adenylyl cyclases play a critical role in generating the cAMP signal required for LTM and L-LTP. Although cAMP may be required for several events in this complex signal transduction cascade, one of the major roles of cAMP may be to support nuclear translocation of Erk/MAP kinase in hippocampal neurons.