Objective: To investigate the presence of autoantibody deposition against type 2 tissue transglutaminase (TG2; a reliable marker of the whole spectrum of gluten sensitivity) in the jejunal tissue and brain of patients with gluten ataxia and in control subjects. Methods: The authors evaluated jejunal biopsy samples from nine patients with gluten ataxia and seven patients with other causes of ataxia for the presence of TG2- related immunoglobulin deposits using double- color immunofluorescence. Autopsy brain tissue from one patient with gluten ataxia and one neurologically intact brain were also studied. Results: IgA deposition on jejunal TG2 was found in the jejunal tissue of all patients with gluten ataxia and in none of the controls. The intestinal IgA deposition pattern was similar to that seen in patients with overt and latent celiac disease and in those with dermatitis herpetiformis. Widespread IgA deposition around vessels was found in the brain of the patient with gluten ataxia but not the control brain. The deposition was most pronounced in the cerebellum, pons, and medulla. Conclusions: Anti- tissue transglutaminase IgA antibodies are present in the gut and brain of patients with gluten ataxia with or without an enteropathy in a similar fashion to patients with celiac disease, latent celiac disease, and dermatitis herpetiformis but not in ataxia control subjects. This finding strengthens the contention that gluten ataxia is immune mediated and belongs to the same spectrum of gluten sensitivity as celiac disease and dermatitis herpetiformis. Objective: To investigate the presence of autoantibody deposition against type 2 tissue transglutaminase (TG2; a reliable marker of the whole spectrum of gluten sensitivity) in the jejunal tissue and brain of patients with gluten ataxia and in controlling subjects. Methods: The authors evaluated jejunal biopsy samples from nine patients with gluten ataxia and seven patients with other causes of ataxia for the presence of TG2-related immunoglobulin deposits using double- color immunofluorescence. Autopsy brain tissue from one patient with gluten ataxia and one neurologically intact brain were also studied. : IgA deposition on jejunal TG2 was found in the jejunal tissue of all patients with gluten ataxia and in none of the controls. The intestinal IgA deposition pattern was similar to that seen in patients with overt and latent celiac disease and in those with dermatitis herpetiformis. Widespread IgA deposition around vessels was found in the brain of the patient with gluten ataxia b ut not the control brain. The deposition was most pronounced in the cerebellum, pons, and medulla. Conclusions: Anti- tissue transglutaminase IgA antibodies are present in the gut and brain of patients with gluten ataxia with or without an enteropathy in similar to patients with celiac disease, latent celiac disease, and dermatitis herpetiformis but not in ataxia control subjects. This finding strengthens the contention that gluten ataxia is immune mediated and belongs to the same spectrum of gluten sensitivity as celiac disease and dermatitis herpetiformis.