Circulating antibodies to gluten fractions have been detected in most patients with celiac disease during gluten ingestion. The various detection techniques, however, are rather complex and inadequate for routine clinical use. Recently, a new indirect immunofluorescent method, named the antigluten antibody (AGA) test, has been developed. To establish the reliability of the test we compared six groups of patients: (1) 15 patients with biopsy-proved celiac disease of whom 13 had positive test results (the other two had already been receiving a gluten-free diet for two to three weeks); (2) 13 malnourished patients without celiac disease who had damaged mucosa, of whom only two had positive test results; (3) 21 patients with celiac symptomatology but normal mucosa, of whom four had positive test results; (4) 42 patients with other intestinal tract diseases, of whom seven had positive test results; (5) 28 patients with extraintestinal diseases, of whom only two had positive test results; and (6) 26 patients with autoimmune diseases, of whom five had positive test results. All patients with celiac disease who had positive test results and who were receiving a gluten-containing diet had titers of 1:40 to 1:80 in the IgG class, while all other patients with positive AGA test results had a low titer of 1:10 to 1:40, in the IgM class mainly. We conclude that the AGA test is an effective screening tool for patients with celiac disease and may serve as a practical index of dietary gluten avoidance.