Cerebrospinal fluid (CSF) is secreted by the choroid plexuses located in the lateral, third and fourth ventricles. The fluid flows through the ventricular system, passing over all the regions of germinal activity. CSF contains growth factors and other neurotrophic factors, which are important for cell survival and proliferation. It has been shown that nerve growth factor deprivation induces apoptosis in the developing cerebral cortex. In this study, disruption of normal CSF flow on neural cell survival in the developing cortex has been investigated. Draining CSF from the ventricles of the brain during development increases the number of neural cell deaths and thinning of the cerebral cortex compared with normal ones. These data from our study indicate that normal CSF circulation is important for the survival of cells in the developing cerebral cortex and thus of CSF in the normal chick cerebral cortex development.