In rat brain, distinct epidermal growth factor-receptor immunoreactivity (EGFR-IR) first appeared in astroglia at about day 16 postnatal, reached maximum intensity at 19 days and then became much weaker as the animals reached adulthood. EGFR-IR was also observed in cerebellar Purkinje cells as early as 11 days postnatal and was maintained into adulthood. In adult and aged animals the most prominent EGF receptor immunostaining occurred in cerebral cortex neurons (layers IV and V) that had the morphology of basket cells. Immunoreactive neurons were abundant in the cingulate, frontal, frontoparietal and striate cortices. In the frontoparietal cortex, EGFR positive neurons were most numerous in the motor area, diminishing laterally towards the somatosensory area. The localization and time of appearance of EGFR-IR did not appear consistent with a direct mitogenic role of the EGF domain in astroglia proliferation during development. However, the EGFR may be involved in neuronal survival and/or neuron-glia signalling.