The aim of this work was to elucidate the possible developmental changes in the offspring lungs induced by administration of monosodium glutamate (MSG) to the pregnant albino rats. Forty pregnant albino rats were used in this study, equally divided into two groups. The first group was the control one, administered distilled water by gastric tube; the second was instead given MSG dissolved in distilled water. The animals were sacrificed at different four days of gestations; 14th (GD14), 16th (GD16), 19th (GD19) and 21st (GD21). Fetal lung sections were stained with Haematoxyline and Eosin (H&E) and with proliferating cell nuclear antigen (PCNA) reactions. The obtained data were statistically analyzed. At GD14, the bronchial tubes started to branch to form small simple primitive bronchiolar tubules. They were lined with pseudo stratified epithelium. At GD16, the bronchial tubes were lined with columnar epithelium with cytoplasmic vacuolization giving a glandular appearance. At GD19, the lining of tubular air spaces was cuboidal epithelium. GD21 showed the formation of secondary crests and appearance of air saccules lined with flat epithelium. Treated animals showed the epithelium of these tubules with desquamation and necrotic cells. Also, there was marked growth retardation in comparison to the control one. The PCNA immune histochemical staining showed high positive immunoreactions in the bronchiolar epithelium and the adjacent stroma. This is more evident in the treated subgroups than in the control ones. It has been concluded that administration of MSG to mothers during pregnancy may exert some growth retardation and histopathological changes in the fetal lungs.