AMPA-type glutamate receptors (AMPARs) mediate most fast excitatory synaptic transmission in the brain. Diversity in excitatory signalling arises, in part, from functional differences among AMPAR subtypes. Although the rapid insertion or deletion of AMPARs is recognised as important for the expression of conventional forms of long-term synaptic plasticity--triggered, for example, by Ca2+ entry through NMDA-type glutamate receptors--only recently has attention focused on novel forms of plasticity that are regulated by, or alter the expression of, Ca2+-permeable AMPARs. The dynamic regulation of these receptors is important for normal synaptic function and in disease states.