Patients who have celiac disease antibodies will have an upper gastrointestinal (GI) endoscopy intestinal biopsy. For this procedure, a flexible tube is inserted into the mouth and down the throat into the stomach and duodenum (the upper part of the small intestine), where a small tissue sample is taken for microscopic examination. Patients with these antibodies will be put on a gluten-free diet and will be followed at NIH every 3 months for 12 months. On the first visit, patients will have their ataxia evaluated using NINDS's ataxia scale and will meet with a dietitian for instructions for a gluten-free diet. On the second through fifth visits (after 3, 6, 9 and 12 months, respectively, on the gluten-free diet), patients will have their ataxia evaluated, speak with a dietitian to assess their nutritional status, weight, and compliance with the diet, and provide a blood sample for celiac disease antibody testing.