Antibodies against gliadin of the IgA class were assessed with an enzyme-linked immunosorbent assay technique in children with celiac disease, healthy blood donors, and adult patients with active Crohn's disease or ulcerative colitis. Significantly higher antibody values were found in celiac children during gluten challenge and during the first 3 months on a gluten-free diet, compared with the findings in the healthy blood donors. The patients with active Crohn's disease had significantly higher levels of IgA antibodies to gliadin than the controls did. Although the highest values were found in patients with celiac disease on a gluten-containing diet, the difference between the means of these two groups was not statistically significant. No correlation was found between disease activity in ulcerative colitis and antibody values. The present results support the view that high levels of IgA-class antibodies against gliadin are indicative of small intestinal disease, especially celiac disease. The variability of the levels of antibodies found among the patients suggests that not only the amount of gluten in the diet but also other factors are important.