The diagnostic value of gliadin antibody determination using the fluorescent immunosorbent test was examined in a prospective study of 57 children with gastrointestinal disease. Antibodies to gliadin were found in all 20 patients with active coeliac disease, whereas 7 of these children (37%) had a normal xylose absorption test despite a flat small gut mucosa. Only 4 (14%) of 28 children with other gastrointestinal conditions had antibodies to gliadin, invariably in low titre. After at least 2 years on a gluten-free diet none of 9 children with coeliac disease in remission had demonstrable gliadin antibodies. The gliadin antibodies disappear slowly, within 6 to 24 months, after withdrawal of gliadin from the diet. 0.8% (5/606) of a healthy control group of children, adolescents and adults (not biopsied) had gliadin antibodies in low titre. Increased mean cow's milk antibody titres were demonstrable in 8 (40%) of 20 patients with active coeliac disease as well as in 9 (32%) of 28 patients with other gastrointestinal lesions. Our studies show that determination of circulating gliadin antibodies is a worthwhile screening test in suspected cases of coeliac disease. In patients so selected there is a definite indication for small intestinal biopsy to confirm the diagnosis.