7 infants diseased with Acrodermatitis enteropathica and 10 normal controls were included in this study. The values of anthranilic acid glucuronide, 6- aminohippuric, anthranilic acid, N-acetyl Kneurine, Kneurine and 30 H Kneurenine, were estimated in mg/24 hours urine, both basal and after tryptophane load. In addition, histopathological and histochemical studies for lactase, succinic dehydrogenase, alkaline phosphatase, acid phosphatase, and alpha-non-specific esterases activities were done for the intestinal mucosal biopsies. All the previous investigations were then repeated after two months treatment with 500 mg/day diiodohydroxyquinoline. The tryptophan metabolites were significantly low in the diseased infants, both basal and after tryptophan load. Moreover, the intestinal enzymes activities were altered. After 2 months treatment with diiodohydroxyquinoline the diseased infants became clinically improved, tryphtophan metabolites became normal, but the activities of the intestinal enzymes were not altered. The biochemical and histochemical findings were discussed, giving the possibility of competitive inhibition of the diiodohydroxyquinolines and the by-product 8 OH Quinololic acid resulting in more degradation of Kneurine and 3 OH Kneurenine to nicotinamide adenine dinucleotide.