Gastrointestinal disorders in children with autism receive little attention. However, symptoms such as abdominal pain, diarrhea, constipation, and flatulence have been considered contributing to the behavioral problems. These symptoms are associated partially with the deficiency of enzymes digesting carbohydrates and inflammation of the gastrointestinal tract. The effect of intestinal inflammation on neurological disorders experienced by autistic children remains unclear. We will study this problem using recently developed non-invasive tests based on two proteins (calprotectin and lactoferrin) analysis in children's stool. Activity of enzymes needed for carbohydrate digestion will be tested in small samples of intestinal tissue. Intestinal permeability will be assessed by measuring urinary excretion of carbohydrate substances (lactulose and rhamnose) administered via the endoscope. This test will help to determine if intestinal inflammation contributes to a "leaky" gut syndrome. The study will provide valuable information for understanding the association between gastrointestinal disease and behavioral problems in autistic children.