Neuronal and glial precursor cells were isolated from primary cultures of embryonic rat mesencephalon. The separation of precursor cells from the neurons was accomplished by the resuspension of the primary cells by trypsinization, followed by replating. This procedure resulted in the death of differentiated neurons and the survival of precursor cells. The survival and proliferation of the replated precursor cells required the presence of epidermal growth factor (EGF) in the culture medium. The precursor cells differentiated into neurons and astrocytes, as determined by immunocytochemical staining with antibodies to neuron specific enolase (NSE) and tau protein or glial fibrillary acidic protein (GFAP) respectively.