An increased prevalence of past tuberculosis is reported in an adult coeliac population. Of 76 adult coeliac disease patients, 6 had had a history of tuberculosis. This compared with the finding of no cases in a population of 81 patients with non-inflammatory bowel diseases, (p = 0.023), which was matched for age, sex, smoking, ethnic origin and social class. The 'expected' number of cases of tuberculosis amongst ACD patients has also been calculated based on local annual notification rates; this was 2.9. Radiological evidence of past tuberculosis was found in 13 (17%) ACD patients, compared with 4 (5%) control patients (p less than 0.05). It is postulated that the increased prevalence of past tuberculosis in ACD patients is the result of depressed cell mediated immunity and/or malnutrition.