Glutamate transporters make a crucial contribution to neuronal signalling by rapidly removing excess glutamate from the synaptic cleft. Here, the authors showed that surface trafficking of the astrocytic glutamate transporter GLT1 (also known as EAAT2) was regulated by neuronal and glial activity. Blocking the surface trafficking of GLT1 altered the kinetics of excitatory postsynaptic currents. Thus, the surface mobility of transporters on astrocytes has an important role in controlling the time course of neurotransmitter action at synapse.