Embryonic neural stem cells (NSCs) were isolated from the neuroepithelium of the dorsal telencephalon of embryonic rats and infected by Ad5-Atoh1-enhanced green fluorescent protein. These NSCs were then delivered into neurosphere culture medium or transplanted into the endolymphatic space of the normal guinea pig cochlea through cochleostomy. Embryonic NSC phenotype of these isolated cells was determined by immunohistochemical detection of cell-specific protein markers. Survival, location and hair cell (HC) differentiation of the implanted NSCs were determined by the expression of the report gene, enhanced green fluorescent protein, and a specific marker for HCs, Myosin VIIa. These implanted cells can survive in the endolymphatic space of the cochlea. Some of the surviving cells differentiated into HCs by Atoh1 gene transfer.