the Institute of Child Health, London sumxARY Thirty-two children with a past diagnosis of coeliac disease were reinvestigated by means of gluten challenge. They had received a gluten-free diet for a mean period of 6 5 years (range 0 25-11 .0) before gluten challenge, and had a mean age of 9 9 years (range 3.0-15.3) at the onset of challenge.Small intestinal biopsies were performed before and after the gluten challenge (at least 10 g natural gluten per day for 3 months in the majority) and, as judged by light microscopy and morphometric techniques, coeliac disease was confirmed in 25 (78%.) of the 32 patients; challenge was continued in the remaining 7 for a total period of 2 years when biopsies were repeated in 6 children and all were normal. Serum and RBC folate, serum iron, Hb level, and clinical symptoms were unpredictable variables in identifying children who developed gluten-induced enteropathies. The social and emotional effects of gluten challenge are discussed. The results highlight the importance of gluten challenge and intestinal biopsy in the diagnosis of coeliac disease and strongly suggest that a normal biopsy after a 3-month gluten challenge (as described above) excludes coeliac disease.Intolerance to dietary gluten is a permanent phenomenon in true coeliac disease (Mortimer et al., 1968;Sheldon, 1969;Young and Pringle, 1971;Hamilton and McNeill, 1972) and there is an increased risk of neoplasia in affected adult patients (Harris et al., 1967;Barry and Read, 1973) which may be reduced by treatment with a strict gluten-free diet (Harris et al., 1967;Holmes et al., 1976). The application of strict diagnostic criteria (Meeuwisse, 1970) is thus of paramount importance to both child and family, and includes demonstration of abnormalities of the small intestinal mucosa induced by the ingestion of gluten. The timing of diagnostic biopsies during a gluten challenge is largely empirical particularly in those patients who remain asymptomatic, and the optimum duration of a gluten challenge has not been established.We present results of a study designed to reappraise a past diagnosis of coeliac disease in a group of children who were being treated with a gluten-free diet. The effects of a gluten challenge on the intestinal mucosa and the clinical, emotional, and haematological effects of the challenge are reported.