<p>Monosodium glutamate (MSG) is a widely used flavor enhancer/food additive around the world. The aim of this investigation was to analyze the effects of MSG administered in ovo on the development of the liver in chicken embryos using histological and immunohistochemical techniques. Four hundred ten fertilized hen’s eggs were categorized into five groups as follows: a control group, a distilled water group, and those containing MSG at three different concentrations, 0.12, 0.6, and 1.2 mg/g egg groups. The test solutions were injected into the yolk of eggs at just prior to incubation. The eggs from each group were opened randomly on the eighteenth and twenty first days of incubation to obtained 6 live embryos, and pieces of liver tissue were obtained. Hematoxylin and eosin, Crossmon's triple staining, and immunohistochemical staining of caspase-3 was performed. Histopathological alterations, including inflammatory cell infiltration and sinusoidal enlargement, were noted in the MSG-treated groups. Furthermore, MSG caused hydropic and vacuolar degenerations in the liver and to induced detachment in the alignment of the Remark cords, and an increased in caspase-3 positivity in the hepatocytes. Finally, it was found that in ovo administered of MSG affect on the embryonic development of the liver.</p>