Insulin-like growth factor-1 (IGF-1) is a potent neurotrophic factor that promotes the proliferation, migration and differentiation of glial and neuronal cells. IGF-1 can also protect neurons from undergoing apoptotic cell death. IGF-1 is produced by the choroid plexus, located in the ventricles. Knowledge of embryonic CSF composition at different developmental stages could be the key to understanding the behavior of neuroepithelial cells (neural stem and progenitor cells). In this study, CSF was aspirated from the lateral ventricle of embryonic mice using micromanipulation and the total concentration of IGF-1 and IGF binding proteins (IGFBPs) was measured on gestational days 12 to 21 (E12-E21). Analysis using Western blot and enzyme-linked immunosorbent assay showed that IGF-1 levels in the CSF decreased from days E12 to E15, increased rapidly from days E16 to E18 and decreased from days E19 to E21. Days E16 to E18 coincide with the onset of neuron proliferation, and migration and organization of the cytoarchitecture of the developing cortex. The concentration of IGFBPs in CSF samples from E12 to E21 did not change. Since CSF is in contact with the cerebral cortical germinal epithelium, changes in CSF IGF-1 concentration could affect the activity of the germinal epithelium and be involved in cerebral cortical development.