Eight autistic patients with steatorrhoea, hypocalciuria, and alleged behavioural improvements on gluten restriction, were fed ordinary diets plus 20 g gluten/day for 4 weeks. None of the patients had any significant change in body-weight or bowel habit as a result of gluten challenge, nor were any histological abnormalities detected on jejunal biopsy. The data suggest that the steatorrhoea and hypocalciuria seen in some autistic subjects cannot be accounted for by the presence of coeliac disease. Furthermore, these patients should not be confined to gluten-free diets, unless rigorous behavioural studies demonstrate a statistically significant improvement in behaviour as a result of the diet, or deterioration during challenge.