the biochemical study of 5 children who were referred to the national center of medical genetics because they were clinically suspected of suffering from an inborn error of the carbohydrate metabolism is presented. thin layer chromatography was carried out to detect these substances in urine and a band was found at the galactose level. a high level of metabolites in blood was found on quantifying them. the final diagnosis consited in demonstrating the deficiency of erythrocytic galactose-1-phosphate uridyltransferase by the spectrophotometric method. the character of carriers of the deficient gene was also proved among the parents of the 5 children.