ABSTRACT Embryonic cerebrospinal fluid (E-CSF) contains many neurotrophic and growth factors, acts as a growth medium for cortical progenitors, and can modulate proliferation and differentiation of neural stem cells. Mesenchymal stem cells (MSCs) are multipotential stem cells that can differentiate into several types of mesenchymal cells as well as nonmesenchymal cells, such as neural cells. In the present study, the effect of E-CSF on proliferation and neural differentiation of bone marrow mesenchymal stem cells (BM-MSCs) was investigated to test whether E-CSF is capable of driving these cells down the neuronal line. To verify the multipotential characteristics of BM-MSCs, the cells were analyzed for their osteogenic and adipogenic potential. Expression of the neural markers, MAP-2 and β-III tubulin, was determined by Immunocytochemistry. BM-MSCs differentiate into neuronal cell types when exposed to b-FGF. BMMSCs cells cultured in medium supplemented with CSF showed significantly elevated proliferation relative to control cells in media alone. E-CSF (E17-E19) supports viability and stimulates proliferation and, significantly, neurogenic differentiation of BM-MSCs. The data presented support an important role for CSF components, specifically neurotrophic factors, in stem cell survival, proliferation and neuronal differentiation. It is crucial to understand this control by CSF to ensure success in neural stem cell therapies.