D-[3H]aspartate (D-Asp) injected into the sensorimotor cortex of the rat resulted in retrograde labelling of thalamic neurones, mainly in the intralaminar and ventromedial nuclei, and the posterior complex. Few cells in the ventrolateral nucleus and ventrobasal complex were labelled. The results show that certain thalamocortical neurones can take up and axonally transport the false transmitter D-Asp, indicating that they might use glutamate or aspartate as transmitter(s).