This study was designed to recognize the biochemical and histological alteration in the liver and kidney of the adult rats (10 weeks old) and infant rats (3 weeks old) as a result to oral intake of some food flavour enhancers. Three treatments were applied, (i) Monosodium glutamate, MSG, (60 mg/kg BW for adult rats, 30 mg/kg BW for infant rats), (ii) Mixture (1:1, w/w) of MSG and 5 inosine monophosphate (5´IMP) and (iii) 5´IMP (30 mg/kg BW for adult rats, 15mg/kg BW for infant rats). The doses administrated to infant rats were increased to the level of adult rats when infant rats reached to the weight of adult age. Significant increments (P>0.05) were recorded in the level of liver function enzymes included ALT, AST, LDH, ALP, and γ-GT in both adult and infant rats due to oral intake of MSG alone. Comparing with the control groups, no significant difference was obtained when the adult and infant rats were treated with 5´IMP alone or its mixture with MSG. The oral intake of MSG alone by the adult and infant rats led to considerable increase in the concentration of creatinine and urea in blood serum as parameter of kidney functions. Urea concentration was the only parameter that indicated significant increment when the infant rates administrated with 5´IMP alone or its mixture with MSG. The histological alterations in the liver and kidney of both adult and infant rats ensure the previous biochemical results. The partial replacement of MSG with 5´IMP led to remarkable reduction in both biochemical and histological alterations induced by MSG. Although the treatment with 5´IMP did not show any biochemical or histological changes in adult rats, hepatic hemorrhage was observed in some of infant rats due to this treatment. It can be recommended that MSG should be minimized in the adult diets by partial replacement with 5´IMP. Also these additives should be totally withdraw from the infant diets.