Neural stem/progenitor cell (NPC) cultures are a tool to study the differentiation of neuronal cells and can be used to model disease conditions in studies investigating the pathological mechanisms affecting the development and cellular plasticity of the central nervous system. There is evidence that abnormalities of NPCs and their differentiation contribute to the pathophysiology of fragile X syndrome. The results obtained with NPC cultures derived from human and mouse brain tissue with the fragile X mutation are in line with the abnormalities of Fmr1-knockout mouse brain in vivo indicating that NPC cultures can be useful as a model for fragile X syndrome.