Long-lasting forms of memory require protein synthesis, but how the pattern of synthesis is related to the storage of a memory has not been determined. Here we show that neural activity directs the mRNA of the Drosophila Ca(2+), Calcium/Calmodulin-dependent Kinase II (CaMKII), to postsynaptic sites, where it is rapidly translated. These features of CaMKII synthesis are recapitulated during the induction of a long-term memory and produce patterns of local protein synthesis specific to the memory. We show that mRNA transport and synaptic protein synthesis are regulated by components of the RISC pathway, including the SDE3 helicase Armitage, which is specifically required for long-lasting memory. Armitage is localized to synapses and lost in a memory-specific pattern that is inversely related to the pattern of synaptic protein synthesis. Therefore, we propose that degradative control of the RISC pathway underlies the pattern of synaptic protein synthesis associated with a stable memory.