In vitro and in vivo studies addressing the differentiation of neural stem and progenitor cells in the CNS require the use of highly specific markers for neurons and gliocytes. The aim of the present work was to study the distribution of a marker for differentiating neurons, i.e., doublecortin (DCX), in structures of the brain and spinal cord in rat embryos during the period preceding the formation of the cortical plate using immunocytochemical methods and light and confocal microscopy. DCX was detected in three types of cell in the developing nervous system at 13-14 days of embryogenesis: neurons giving reactions for the nuclear marker for differentiated nerve cells NeuN, migrating and differentiating neuroblasts, and some cells which are members of the population of radial gliocytes. The quite high selectivity of DCX expression allows use of this marker to be recommended for studies of the early stages of nervous system development in mammals.