Gastrointestinal permeability was assessed by means of absorption of 51 Cr-labelled EDTA in 24 patients with schizophrenia (12 in relapse and 12 in remission). The results were compared with those for patients with coeliac disease and those for normal controls. Significant differences between the schizophrenic patients and the normal controls were not established. The results for the schizophrenic patients in remission were no different from those for the patients in relapse, and there was no evidence from the study of an effect on gastrointestinal permeability of either anticholinergic or antidepressant medication. It is concluded that schizophrenia is, at least in the majority of cases, unrelated to coeliac disease.