The effect of an elemental diet (Vivonex) together with a gluten-free diet on the absorption of water, sodium and chloride in the jejunum was studied in 4 patients with untreated adult coeliac disease before and after a 1-month course of therapy. The morphology of the jejunum was also studied by jejunal biopsy taken at the same time as the intestinal perfusion. The results were compared with those obtained in 4 patients with adult coeliac disease treated with a gluten-free diet alone. No marked improvement was noted in the transportation of water, sodium and chloride after either treatment with Vivonex and a gluten-free diet or after a gluten-free diet alone, and no marked histological changes were found. Clinical improvement occurred in both groups of patients, in that the diarrhoea improved in all patients and they generally felt better. There appears to be no additional advantage of using an elemental diet with a gluten-free diet in the initial management of adult coeliac disease.