Data on biochemical study of a patient with glycogenosis of the III type (limit dextrinosis) are presented. In a punctate of liver tissue absence of amylo-1,6-glucosidase activity and significant accumulation of glycogen, which was anomalous in structure, were noted. Loading with galactose and adrenaline caused alterations typical for the III type of glycogenosis. Content of glucose and lactate in blood were also studied in response to the peroral administration of glucose and protein. In erythrocytes of the patient the polysaccharide structure was shown to be anomalous; it resembled the structure of a polysaccharide from liver tissue of the patient.